Scriptures:

Genesis 6:1-2 – Now it came to pass, when men began to multiply on the face of the earth, and daughters were born to them, that the sons of God saw the daughters of men, that they were beautiful; and they took wives for themselves of all whom they chose. 

Genesis 6:4 – There were giants on the earth in those days, and also afterward, when the sons of God came in to the daughters of men and they bore children to them. Those were the mighty men who were of old, men of renown.

Job 1:6 – Now there was a day when the sons of God came to present themselves before the Lord, and Satan also came among them.

Job 38:6–7 – On what were its bases sunk, or who laid its cornerstone, when the morning stars sang together and all the sons of God shouted for joy?

2 Peter 2:4-10 – For if God did not spare the angels who sinned, but cast them down to Tartarus and committed them into chains of darkness, to be reserved for judgment; and did not spare the ancient world, but saved Noah, one of eight people, a preacher of righteousness, bringing in the flood on the world of the ungodly; and turning the cities of Sodom and Gomorrah into ashes, condemned them to destruction, making them an example to those who afterward would live ungodly; and delivered righteous Lot, who was oppressed by the filthy conduct of the wicked (for that righteous man, dwelling among them, tormented his righteous soul from day to day by seeing and hearing their lawless deeds)— then the Lord knows how to deliver the godly out of temptations and to reserve the unjust under punishment for the day of judgment,  and especially those who walk according to the flesh in the lust of uncleanness and despise authority.

Jude 1:5-7 – But I want to remind you, though you once knew this, that the Lord, having saved the people out of the land of Egypt, afterward destroyed those who did not believe. And the angels who did not keep their proper domain, but left their own abode, He has reserved in everlasting chains under darkness for the judgment of the great day; as Sodom and Gomorrah, and the cities around them in a similar manner to these, having given themselves over to sexual immorality and gone after strange flesh, are set forth as an example, suffering the vengeance of eternal fire.

Jude 1:14-15 – Now Enoch, the seventh from Adam, prophesied about these men also, saying, “Behold, the Lord comes with ten thousands of His saints, to execute judgment on all, to convict all who are ungodly among them of all their ungodly deeds which they have committed in an ungodly way, and of all the harsh things which ungodly sinners have spoken against Him.”

Enoch 7:1-2 – It happened after the sons of men had multiplied in those days, that daughters were born to them, elegant and beautiful. And when the angels, the sons of heaven, beheld them, they became enamoured of them, saying to each other, “Come, let us select for ourselves wives from the progeny of men, and let us beget children.”

Enoch 7:10-15 – Then they took wives, each choosing for himself; whom they began to approach, and with whom they cohabited; teaching them sorcery, incantations, and the dividing of roots and trees. And the women conceiving brought forth giants, whose stature was each three hundred cubits. These devoured all which the labor of men produced; until it became impossible to feed them; when they turned themselves against men, in order to devour them; and began to injure birds, beasts, reptiles, and fishes, to eat their flesh one after another, and to drink their blood. Then the earth reproved the unrighteous.

Enoch 10:6-9 – Again the Lord said to Raphael, “Bind Azazyel hand and foot; cast him into darkness; and opening the desert which is in Dudael, cast him in there. Throw upon him hurled and pointed stones, covering him with darkness; there shall he remain forever; cover his face, that he may not see the light. And in the great day of judgment let him be cast into the fire.”

Church Fathers

The Apostle Peter / Clement of Rome:

“But when, having assumed these forms, they convicted as covetous those who stole them, and changed themselves into the nature of men, in order that, living holily, and showing the possibility of so living, they might subject the ungrateful to punishment, yet having become in all respects men, they also partook of human lust, and being brought under its subjection they fell into cohabitation with women; and being involved with them, and sunk into defilement and altogether emptied of their power, were unable to turn back to the first purity of their proper nature, their members turned away from their fiery substance: for the fire itself, being exhausted by the weight of lust, and changed into flesh, they trode the impious path downward. For they themselves, being fettered with bonds of flesh, were constrained and strongly bound; wherefore they have no more been able to ascend into the heavens.” – Peter (quoted by Clement of Rome), Clementine Homilies, Homily 8, Chapter 8

All things therefore being completed which are in heaven, and in earth, and in the waters, and the human race also having multiplied, in the eighth generation, righteous men, who had lived the life of angels, being allured by the beauty of women, fell into promiscuous and illicit connections with these; and thenceforth acting in all things without discretion, and disorderly, they changed the state of human affairs and the divinely prescribed order of life, so that either by persuasion or force they compelled all men to sin against God their Creator. In the ninth generation are born the giants, so called from of old, not dragon-footed, as the fables of the Greeks relate, but men of immense bodies, whose bones, of enormous size, are still shown in some places for confirmation. But against these the righteous providence of God brought a flood upon the world, that the earth might be purified from their pollution, and every place might be turned into a sea by the destruction of the wicked. – Peter (quoted by Clement of Rome), Recognitions of Clement, Book 1, Chapter 29

Barnabas:

It therefore behooves us, who inquire much concerning events at hand, to search diligently into those things which are able to save us. Let us then utterly flee from all the works of iniquity, lest these should take hold of us; and let us hate the error of the present time, that we may set our love on the world to come: let us not give loose reins to our soul, that it should have power to run with sinners and the wicked, lest we become like them. The final stumbling-block (or source of danger) approaches, concerning which it is written, as Enoch says, “For for this end the Lord has cut short the times and the days, that His Beloved may hasten; and He will come to the inheritance.” – Letter of Barnabas, chapter 4

Justin Martyr:

But if this idea take possession of some one, that if we acknowledge God as our helper, we should not, as we say, be oppressed and persecuted by the wicked; this, too, I will solve. God, when He had made the whole world, and subjected things earthly to man, and arranged the heavenly elements for the increase of fruits and rotation of the seasons, and appointed this divine law — for these things also He evidently made for man — committed the care of men and of all things under heaven to angels whom He appointed over them. But the angels transgressed this appointment, and were captivated by love of women, and begot children who are those that are called demons; and besides, they afterwards subdued the human race to themselves, partly by magical writings, and partly by fears and the punishments they occasioned, and partly by teaching them to offer sacrifices, and incense, and libations, of which things they stood in need after they were enslaved by lustful passions; and among men they sowed murders, wars, adulteries, intemperate deeds, and all wickedness. Whence also the poets and mythologists, not knowing that it was the angels and those demons who had been begotten by them that did these things to men, and women, and cities, and nations, which they related, ascribed them to god himself, and to those who were accounted to be his very offspring, and to the offspring of those who were called his brothers, Neptune and Pluto, and to the children again of these their offspring. For whatever name each of the angels had given to himself and his children, by that name they called them. – Justin Martyr, Second Apology, chapter 5

Why, then, should this be? In our case, who pledge ourselves to do no wickedness, nor to hold these atheistic opinions, you do not examine the charges made against us; but, yielding to unreasoning passion, and to the instigation of evil demons, you punish us without consideration or judgment. For the truth shall be spoken; since of old these evil demons, effecting apparitions of themselves, both defiled women and corrupted boys, and showed such fearful sights to men, that those who did not use their reason in judging of the actions that were done, were struck with terror; and being carried away by fear, and not knowing that these were demons, they called them gods, and gave to each the name which each of the demons chose for himself. – Justin Martyr, First Apology, chapter 5

Athenagoras:

The other angels were created by Him, and entrusted with the control of matter and the forms of matter….  Just as with men, they have freedom of choice as to both virtue and vice…. Some men are diligent in the matters entrusted to them by you, and others are faithless. It is the same among the angels. They are free agents, being created that way by God, as you will observe. Some of them have continued in those things for which God had made them. They have remained over the things to which He had ordained them. But some outraged both the constitution of their nature and the oversight entrusted to them….  These angels fell into impure love of virgins and were subjugated by the flesh…. Those who are called giants were begotten from these lovers of virgins. – Athenagoras (c. 175, E), 2.142.

These angels, then, who have fallen from heaven, and haunt the air and the earth, and are no longer able to rise to heavenly things, and the souls of the giants, who are the demons who wander about the world, perform similar actions. – Athenagoras (c. 175, E), 2.142.

Irenaeus:

“And for a very long while wickedness extended and spread, and reached and laid hold upon the whole race of mankind, until a very small seed of righteousness remained among them and illicit unions took place upon the earth, since angels were united with the daughters of the race of mankind; and they bore to them sons who for their exceeding greatness were called giants.” – Irenaeus, Demonstration of Apostolic Preaching, Chapter 18

Since the Son of God is always one and the same, He gives to those who believe on Him a well of water [springing up] to eternal life, but He causes the unfruitful fig-tree immediately to dry up; and in the days of Noah He justly brought on the deluge for the purpose of extinguishing that most infamous race of men then existent, who could not bring forth fruit to God, since the angels that sinned had commingled with them, and [acted as He did] in order that He might put a check upon the sins of these men, but [that at the same time] He might preserve the archetype, the formation of Adam. – Irenæus, Against Heresies Book IV, Chapter XXXVI

And that man was not justified by these things, but that they were given as a sign to the people, this fact shows,— that Abraham himself, without circumcision and without observance of Sabbaths, “believed God, and it was imputed unto him for righteousness; and he was called the friend of God.”39913991 Jas. ii. 23. Then, again, Lot, without circumcision, was brought out from Sodom, receiving salvation from God. So also did Noah, pleasing God, although he was uncircumcised, receive the dimensions [of the ark], of the world of the second race [of men]. Enoch, too, pleasing God, without circumcision, discharged the office of God’s legate to the angels although he was a man, and was translated, and is preserved until now as a witness of the just judgment of God, because the angels when they had transgressed fell to the earth for judgment, but the man who pleased [God] was translated for salvation. Moreover, all the rest of the multitude of those righteous men who lived before Abraham, and of those patriarchs who preceded Moses, were justified independently of the things above mentioned, and without the law of Moses. As also Moses himself says to the people in Deuteronomy: “The Lord thy God formed a covenant in Horeb. The Lord formed not this covenant with your fathers, but for you.” – Irenaeus, Against Heresies, Book 4, Chapter 16

Enoch, too, pleasing God, without circumcision, discharged the office of God’s legate to the angels although he was a man, and was translated, and is preserved until now as a witness of the just judgment of God, because the angels when they had transgressed fell to the earth for judgment, but the man who pleased [God] was translated for salvation. – Irenaeus, Against Heresies, book 4, chapter 16, part 2

Clement of Alexandria:

The mind is led astray by pleasure, and the virgin center of the mind, if not disciplined by the Word, degenerates into licentiousness and reaps disintegration as reward for its transgressions. An example of this for you is the angels who forsook the beauty of God for perishable beauty and fell as far as heaven is from the earth. – Clement of Alexandria, CHRIST THE EDUCATOR 3.2.14

Bardesanes:

It will therefore be manifest to you, that the goodness of God is great toward man, and that freedom has been given to him in greater measure than to any of those elemental bodies of which we have spoken, in order that by this freedom he may justify himself, and order his conduct in a godlike manner, and be copartner with angels, who are likewise possessed of personal freedom. For we are sure that, if the angels likewise had not been possessed of personal freedom, they would not have consorted with the daughters of men, and sinned, and fallen from their places. In like manner, too, those other angels, who did the will of their Lord, were, by reason of their self-control, raised to higher rank, and sanctified, and received noble gifts. For every being in existence is in need of the Lord of all; of His gifts also there is no end. – Bardesanes, The Book of the Laws of Various Countries, chapter 1

Tertullian:

By our sacred books, we are instructed how from certain angels, who fell of their own free will, there sprang an even more wicked demon brood. – Tertullian (c. 197, W), 3.36.

Those angels who invented them [jewelry, etc.] are assigned under condemnation to the penalty of death. They are the same angels who rushed from heaven on the daughters of men. . . . If it is true, they laid bare the operations of metallurgy, divulged the natural properties of herbs, promulgated the powers of enchantments, and traced out every curiosity, even to the interpretation of the stars. They conferred appropriately—and as it were, peculiarly—upon women that instrumental means of womanly ostentation: the radiances of jewels, . . . the dyes of orchil with which wools are dyed, and that black powder itself with which the eyelids and eyelashes are made prominent. – Tertullian (c. 198, W), 4.14, 15.

I lay down this one proposition: that those angels—the deserters from God, the lovers of women—were likewise the discoverers of this curious art [of astrology]. And on that account, they were also condemned by God. . . . For we know the mutual alliance of magic and astrology. – Tertullian (c. 200, W), 3.65.

For indeed it is “on account of the angels” that he said women must be veiled, because on account of “the daughters of men” angels revolted from God. – Tertullian, On Prayer, chapter 22

He adds: “Because of the angels.” What angels? In other words, whose angels? If he means the fallen angels of the Creator, there is great propriety in his meaning. It is right that that face which was a snare to them should wear some mark of a humble guise and obscured beauty. – Tertullian, Against Marcion, Book 5, chapter 8

The contraries, at all events, of all these (considerations) effect that a man is not to cover his head: to wit, because he has not by nature been gifted with excess of hair; because to be shaven or shorn is not shameful to him; because it was not on his account that the angels transgressed. – Tertullian, On The Veiling of Virgins, chapter 8

I am aware that the Scripture of Enoch, which has assigned this order (of action) to angels, is not received by some, because it is not admitted into the Jewish canon either. I suppose they did not think that, having been published before the deluge, it could have safely survived that world-wide calamity, the abolisher of all things. If that is the reason (for rejecting it), let them recall to their memory that Noah, the survivor of the deluge, was the great-grandson of Enoch himself; and he, of course, had heard and remembered, from domestic renown and hereditary tradition, concerning his own great-grandfather’s grace in the sight of God, and concerning all his preachings; since Enoch had given no other charge to Methuselah than that he should hand on the knowledge of them to his posterity. Noah therefore, no doubt, might have succeeded in the trusteeship of (his) preaching; or, had the case been otherwise, he would not have been silent alike concerning the disposition (of things) made by God, his Preserver, and concerning the particular glory of his own house. If (Noah) had not had this (conservative power) by so short a route, there would (still) be this (consideration) to warrant our assertion of (the genuineness of) this Scripture: he could equally have renewed it, under the Spirit’s inspiration, after it had been destroyed by the violence of the deluge, as, after the destruction of Jerusalem by the Babylonian storming of it, every document of the Jewish literature is generally agreed to have been restored through Ezra. But since Enoch in the same Scripture has preached likewise concerning the Lord, nothing at all must be rejected by us which pertains to us; and we read that every Scripture suitable for edification is divinely inspired. By the Jews it may now seem to have been rejected for that (very) reason, just like all the other (portions) nearly which tell of Christ. Nor, of course, is this fact wonderful, that they did not receive some Scriptures which spoke of Him whom even in person, speaking in their presence, they were not to receive. To these considerations is added the fact that Enoch possesses a testimony in the Apostle Jude. – Tertullian, On The Apparel of Women, book 1, chapter 3

Origen:

But not only did man fall from perfection to imperfection, but so too did “the sons of God,” “when they saw that the daughters of men were fair, and took for themselves whomever they chose.” – Origen, Commentary on John, Book 13.243

In my opinion, however, it is certain wicked demons, and, so to speak, of the race of Titans or Giants, who have been guilty of impiety towards the true God, and towards the angels in heaven, and who have fallen from it, and who haunt the denser parts of bodies, and frequent unclean places upon earth, and who, possessing some power of distinguishing future events, because they are without bodies of earthly material, engage in an employment of this kind, and desiring to lead the human race away from the true God, secretly enter the bodies of the more rapacious and savage and wicked of animals, and stir them up to do whatever they choose, and at whatever time they choose…. – Origen, Against Celsus, book 4, chapter 92 (c. 248), 4.538.

For even in that little treatise called The Pastor or Angel of Repentance, composed by Hermas, we have the following: “First of all, believe that there is one God who created and arranged all things; who, when nothing formerly existed, caused all things to be; who Himself contains all things, but Himself is contained by none.” And in the book of Enoch also we have similar descriptions. – Origen, On First Principles, book 1, chapter 3, part 3

Enoch also, in his book, speaks as follows: “I have walked on even to imperfection;” which expression I consider may be understood in a similar manner, viz, that the mind of the prophet preceded in its scrutinity and investigation of all visible things, until it arrived at that first beginning in which it beheld imperfect matter (existing) without “qualities.” For it is written in the same book of Enoch, “I beheld the whole of matter;” which is so understood as if he had said: “I have clearly seen all of the divisions of matter which are broken up from one into each individual species either of men, or animals, or of the sky, or of the sun, or of all other things in this world.” – Origen, On First Principles, book 4, chapter 1, part 35

Apostate and refugee powers that have departed from God—because of the very wickedness of their mind and will, or from envy … invented many errors and delusions of false doctrine in order to prevent any progress. – Origen (c. 225), 4.336.

It is true of all demons that they were not originally demons. Rather, they became so in departing from the true way. Accordingly, the name “demon” is given to those beings who have fallen away from God. – Origen (c. 248), 4.638.

Commodianus:

Such was the beauty of women that it turned the angels aside. As a result, being contaminated, they could not return to heaven. Being rebels from God, they uttered words against Him. Then the Highest uttered His judgment against them. And from their seed, giants are said to have been born. By them, arts were made known in the earth. They taught the dyeing of wool and everything that is done. When they died, men erected images to them. Yet, because they were of an evil seed, the Almighty did not approve of their being brought back from death when they had died. For that reason, they wander and they now subvert many bodies. And it is these whom you [pagans] presently worship and pray to as gods. – Commodianus (c. 240, W), 4.203.

Julius Africanus:

When men multiplied on the earth, the angels of heaven came together with the daughters of men. In some copies I found “the sons of God.” What is meant by the Spirit, in my opinion, is that the descendants of Seth are called the sons of God on account of the righteous men and patriarchs who have sprung from him, even down to the Saviour Himself; but that the descendants of Cain are named the seed of men, as having nothing divine in them, on account of the wickedness of their race and the inequality of their nature, being a mixed people, and having stirred the indignation of God. But if it is thought that these refer to angels, we must take them to be those who deal with magic and jugglery, who taught the women the motions of the stars and the knowledge of things celestial, by whose power they conceived the giants as their children, by whom wickedness came to its height on the earth, until God decreed that the whole race of the living should perish in their impiety by the deluge. – Julius Africanus (c. 245, E), Fragments of the Five Books of the Chronography of Julius Africanus, Fragment 2

Cyprian:

All of these things [i.e., the making of jewelry] the sinning and apostate angels put forth by their arts, when, lowered to the contagions of earth, they forsook their heavenly vigor. They also taught women to paint the eyes with blackness drawn around them in a circle and to stain the cheeks with a deceitful red. – Cyprian (c. 250, W), 5.434.

Lactantius:

God, in His foresight, sent angels for the protection and improvement of the human race—lest the devil . . . should either corrupt or destroy men through his subtlety. Since He had given these angels a free will, He admonished them above all things not to defile themselves with contamination from the earth and thus lose the dignity of their heavenly nature. . . . However, while the angels lived among men, that most deceitful ruler of the earth, by his very association, gradually enticed them to vices and polluted them through sexual relations with women. Thereafter, not being admitted into heaven because of the sins into which they had plunged themselves, they fell to the earth. – Lactantius (c. 304–313, W), 7.64.

They strive to turn men away from the worship and knowledge of the true Majesty, so men will not be able to obtain immortality. That is because these angels lost [immortality] because of their wickedness. – Lactantius (c. 304–313, W), 7.66.

Although they are the destroyers of men, they wish to appear as men’s guardians—so that they themselves will be worshipped and so that God will not be worshipped. – Lactantius (c. 304-313), 7.64.

However, those who were born from [the relations of angels with women]—because they were neither angels nor men, but had a mixed nature—were not admitted into Hades [when they died]. Similarly, their fathers had not been admitted into heaven, either. Thus there came to be two kinds of demons: one of heaven, the other of the earth. The latter are the wicked spirits, who are the authors of all the evils that are done. This same devil is their prince…. However, grammarians say that the reason they are called demons… is because they are skilled and acquainted with matters. For the grammarians think they are gods. In truth, the demons are acquainted with some future events, but not with all. For He has not permitted them to know entirely the counsel of God…. – Lactantius (c. 304-313), 7.64; extended discussion: 4.328-4.334

Archelaus:

Certain of the angels, refusing to submit themselves to the commandment of God, resisted His will. And one of them indeed fell like a flash of lightning upon the earth, while others, harassed by the dragon, sought pleasure in sexual relations with the daughters of men, and thus brought on themselves the deserved recompense of the punishment of eternal fire. – Disputation of Archelaus and Manes (c. 320, E), 6.205.

Eusebius:

But when they did nothing of this kind, but tried to make supplication to the evil daemons by a foul and licentious life and unseemly words, and by feeding on raw flesh, and rending victims asunder, and by human sacrifices, how was it even possible that doing such deeds, and pursuing practices pleasing to the wicked, they should be received as friends by the Supreme God, or by the divine Powers subject to Him, or by any good beings at all? But in fact it is manifest to all that he who practises the things that are dear to the wicked can never be a friend of the good. So then it was not to gods, nor yet to good daemons, but only to the wicked, that those of whom I have spoken paid worship. And this argument is still further confirmed by Plutarch, in the passage where he says that the mythical narratives told as concerning gods are certain tales about daemons, and the deeds of Giants and Titans celebrated in song among the Greeks are also stories about daemons, intended to suggest a new phase of thought. Of this kind then perhaps were the statements in the Sacred Scripture concerning the giants before the flood, and those concerning their progenitors, of whom it is said, “And when the angels of God saw the daughters of men that they were fair, they took unto them wives of all that they chose,” and of these were born “the giants the men of renown which were of old.” For one might say that these daemons are those giants, and that their spirits have been deified by the subsequent generations of men, and that their battles, and their quarrels among themselves, and their wars are the subjects of these legends that are told as of gods. – Eusebius of Caesarea, Preparation for the Gospel, Book 5, Chapter 4

Ambrose of Milan:

“The giants (Nephilim) were on the Earth in those days.” The author of the divine Scripture does not mean that those giants must be considered, according to the tradition of poets, as sons of the earth but asserts that those whom he defines with such a name because of the extraordinary size of their body were generated by angels and women. — Ambrose, on Noah, 4.8. Genesis 1–11

Didymus the Blind:

Genesis 4:1-2 “Adam knew Eve his wife, and she conceived and bore Cain, and she said: “I have acquired a man through God.” And she again bore his brother Abel. Abel became a shepherd of sheep, but Cain worked the ground.” Following the expulsion from Paradise and the making of the leather tunics, it is said: “Adam knew Eve his wife,” where “knowing” is said instead of “having experience of” or “having relations with” a woman. For he knew her in the sense of understanding or being acquainted with her. Thus he also said when he saw her: “This now is bone of my bones.” And regarding the knowledge by which Adam knew Eve his wife, it is also said in the Books of Kings: “Elkanah knew Hannah his wife.” Likewise it is said of Rebekah: “She was a virgin, and no man had known her,” meaning not that no one had ever known her in any way, but clearly that she had not yet been joined to a man. Well and fittingly it says: “She was a virgin, and no man had known her”; unless it is understood intelligently, it could seem redundant, but the phrase intends to indicate that she was most pure both in body and in mind. In this divine manner also Mary said: “How shall this be to me, since I do not know a man?” For being unacquainted with the sight of a man, she was disturbed when she saw the angel, unless he himself removed her fear. And it is plausible to think that, being knowledgeable of the Law, she considered whether the one appearing was perhaps one of the fallen angels, of whom it is said that they desired the daughters of men. – Didymus the Blind, Commentary on Genesis 4:1-2

Jerome:

Moreover there were giants on the earth in those days; and after these things, as the sons of God were accustomed to go in to the daughters of men, so they would breed with them. Those were the giants from of old, men called by name. In the Hebrew, it has the following: “Falling ones” (that is, annaphilim) were on the earth in those days. And after these things, when the sons of the gods used to go in to the daughters of men and breed with them, these were the mighty ones from the beginning, men called by name. Instead of falling ones or giants, Symmachus translated ‘violent ones’. The name “failing ones” is indeed fitting both for angels and for the offspring of holy ones. – Jerome, Hebrew Questions on Genesis 6.4

Other References:

Jubilees 5:1-2 – And it came to pass when the children of men began to multiply on the face of the earth and daughters were born unto them, that the angels of God saw them on a certain year of this jubilee, that they were beautiful to look upon; and they took themselves wives of all whom they chose, and they bare unto them sons and they were giants. And lawlessness increased on the earth and all flesh corrupted its way, alike men and cattle and beasts and birds and everything that walks on the earth – all of them corrupted their ways and their orders, and they began to devour each other, and lawlessness increased on the earth and every imagination of the thoughts of all men (was) thus evil continually.

Jubilees 4:22 – And he testified to the Watchers, who had sinned with the daughters of men; for these had begun to unite themselves, so as to be defiled, with the daughters of men, and Enoch testified against (them) all.

Hurtful are women, my children; because, since they have no power or strength over the man, they act subtly through outward guise how they may draw him to themselves; and whom they cannot overcome by strength, him they overcome by craft. For moreover the angel of God told me concerning them, and taught me that women are overcome by the spirit of fornication more than men, and they devise in their heart against men; and by means of their adornment they deceive first their minds, and instill the poison by the glance of their eye, and then they take them captive by their doings, for a woman cannot overcome a man by force. Therefore flee fornication, my children, and command your wives and your daughters that they adorn not their heads and their faces; because every woman who acts deceitfully in these things has been reserved to everlasting punishment. For thus they allured the Watchers before the flood; and as these continually beheld them, they fell into desire each of the other, and they conceived the act in their mind, and changed themselves into the shape of men, and appeared to them in their congress with their husbands; and the women, having in their minds desire toward their apparitions, gave birth to giants, for the Watchers appeared to them as reaching even unto heaven. – Testament of Reuben, chapter 5

On what principle it was that giants were born of angels and women? (Genesis 6:4): But he [Moses] relates that these giants were sprung from a combined procreation of two natures, namely, from angels and mortal women; for the substance of angels is spiritual; but it occurs every now and then that on emergencies occurring they have imitated the appearance of men, and transformed themselves so as to assume the human shape; as they did on this occasion, when forming connections with women for the production of giants. But if the children turn out imitators of the wickedness of their mothers, departing from the virtue of their fathers, let them depart, according to the determination of the will of a depraved race, and because of their proud contempt for the supreme Deity, and so be condemned as guilty of voluntary and deliberate wickedness. But sometimes Moses styles the angels the sons of God, inasmuch as they were not produced by any mortal, but are incorporeal, as being spirits destitute of any body. – Philo of Alexandria, Questions, question 92

“And when the angels of God saw the daughters of men that they were beautiful, they took unto themselves wives of all of them whom they Chose.” (Genesis 6:2.} Those beings, whom other philosophers call demons, Moses usually calls angels; and they are souls hovering in the air. And let no one suppose, that what is here stated is a fable, for it is necessarily true that the universe must be filled with living things in all its parts, since every one of its primary and elementary portions contains its appropriate animals and such as are consistent with its nature; –the earth containing terrestrial animals, the sea and the rivers containing aquatic animals, and the fire such as are born in the fire…. – Philo of Alexandra, On The Giants, chapter 2

For many angels of God accompanied with women, and begat sons that proved unjust, and despisers of all that was good, on account of the confidence they had in their own strength; for the tradition is, that these men did what resembled the acts of those whom the Grecians call giants. But Noah was very uneasy at what they did; and being displeased at their conduct, persuaded them to change their dispositions and their acts for the better: but seeing they did not yield to him, but were slaves to their wicked pleasures, he was afraid they would kill him, together with his wife and children, and those they had married; so he departed out of that land. – Josephus, Antiquities of the Jews, Book 1, Chapter 3, Section 1

And it came to pass when the sons of men began to multiply on the face of the ground, and beautiful daughters were born to them, that the sons of the great ones saw that the daughters of men were beautiful, with eyes painted and hair curled, walking with uncovered flesh, and they conceived lustful thoughts; and they took them wives of all they chose. . . . Shamhazai and Azael fell from heaven and were on earth in those days, and also after that, when the sons of the great ones came in unto the daughters of men, and they bare children to them: the same are called men of the world, the men of renown. – Targum Pseudo-Jonathan 6:1–4

2 Baruch 56:10-15 – For he became a danger to his own soul, even to the angels. For, moreover, at that time when he was created, they enjoyed liberty. And became he a danger some of them descended, and mingled with the women. And then those who did so were tormented in chains. But the rest of the multitude of the angels, of which there is (no) number, restrained themselves. And those who dwelt on the earth perished together (with them) through the waters of the deluge.

“The great Giants with gleaming armour… [and later] bound… in bitter chains… as far beneath the earth to Tartarus.” – Hesiod (700 BC), The Theogony 176–182; 713–719

The Big Reversal:

From Adam Seth was born, who was the third after Abel, and from Seth Enosh was born. He hoped to be called the Lord and God. Therefore the children born from him bear the name ‘sons of God’, just like we also from the name of the master Christ are called Christians. The race of Seth was segregated and not mixed with the race of Cain because of the curse which was laid on him by the God of the universe. But later, when they observed how beautiful the daughters of Cain’s family were, they became enchanted and took them for themselves as wives, thus ruining their ancestral nobility. – Athanasius of Alexandria, Interpretationes ex Veto Testamento, Quaestio 65

He called the sons of Seth sons of God, those who, like the sons of Seth, had been called “the righteous people of God.” The beautiful daughters of men whom they saw were the daughters of Cain who adorned themselves and became a snare to the eyes of the sons of Seth. Then Moses said, they took them wives of all which they chose. – Ephrem the Syrian, Commentary on Genesis, pages 134-135

“Now, when the sons of God saw that the daughters of men were beautiful, they took wives for themselves from them all just as they were inclined.” Let us study each expression of this statement closely so that nothing of what is hidden below the surface may pass us by. You see, there is need to make a careful study of this passage and confute the fanciful interpretations of those people whose every remark is made rashly – firstly, to repeat what they presume to say, and by demonstrating the absurdity of what is said by them to teach your good selves the true sense of Scripture so that you will not lend your ears idly to people uttering those blasphemies and presuming to speak in a way that brings their own persons into jeopardy. I mean, they claim that this remark is made not about human being but about angels; these (they say) he called sons of God. Let them demonstrate firstly where angels are called sons of God; they would not, however, be able to show this anywhere. While human beings are called sons of God, angels are nowhere so called. On the contrary, it speaks about angels in these terms: “He makes the winds his angels, fire and flame his ministers,” whereas about human beings, “I said, You are gods,” and again, “Sons have I begotten and raised,” and again, “Israel my firstborn son” – but an angel is nowhere called son, or son of God. What in fact do they claim? To be sure, they really were angels, but because they fell into this lawless way, they lost their status…. Is it not a particular hallmark of folly to claim that angels descended to have intercourse with women, and that incorporeal nature of theirs was reduced to association with corporeal creatures? Or do you not hear the words of Christ about the being of angels, “At the resurrection they neither marry nor are given in marriage, but are like angels of God”? After all, it is not for that kind of incorporeal creature to ever feel the onset of desire. In response to these people we have to reach the same conclusion, that to admit this notion into one’s mind is the height of absurdity. We made the point before in teaching you that it is customary with Scripture to call human beings sons of God. So since these people took their origin from Seth and from his son named Enosh (the text, remember, saying, “He it was who hoped to invoke the name of the Lord God”), those descended from him in the future were called sons of God by Sacred Scripture for the reason of their imitation of the virtue of their ancestors up to his time. On the other hand, he gave the name sons of men to those born after Seth, the descendants of Cain and those taking their descent from him. – John Chrysostom, Homily 22 on Genesis

That we rightly understand this passage is also very much confirmed by the interpretation of the other translators. Aquila says: ‘When the sons of the gods saw the daughters of men’. On the other hand, instead of ‘sons of the gods’, Symmachus rendered the expression as ‘sons of the rulers’. They called the descendants of Seth and of Enosh sons of the gods, or better, sons of the rulers, because of the piety and godliness which was in them, and because they could defeat all adversaries: while God, I suppose, in all likelihood came to their aid, and made known all around this pious and holy generation, which was not mixed with that other one, that is to say, with the descendants from Cain and, what is more, from Lamech. – Cyril of Alexandria, Glaphyra in Genesim 2.1

When the human race, in the exercise of this freedom of will, increased and advanced, there arose a mixture and confusion of the two cities by their participation in a common iniquity. And this calamity, as well as the first, was occasioned by woman, though not in the same way; for these women were not themselves betrayed, neither did they persuade the men to sin, but having belonged to the earthly city and society of the earthly, they had been of corrupt manners from the first, and were loved for their bodily beauty by the sons of God, or the citizens of the other city which sojourns in this world.

In the third book of this work we made a passing reference to this question, but did not decide whether angels, inasmuch as they are spirits, could have bodily intercourse with women. For it is written, “Who makes His angels spirits,” that is, He makes those who are by nature spirits His angels by appointing them to the duty of bearing His messages. For the Greek word ἄγγελος, which in Latin appears as “angelus,” means a messenger…. From these assertions, indeed, I dare not determine whether there be some spirits embodied in an aerial substance (for this element, even when agitated by a fan, is sensibly felt by the body), and who are capable of lust and of mingling sensibly with women; but certainly I could by no means believe that God’s holy angels could at that time have so fallen, nor can I think that it is of them the Apostle Peter said, “For if God spared not the angels that sinned, but cast them down to hell, and delivered them into chains of darkness, to be reserved unto judgment.” [2 Peter 2:4] I think he rather speaks of these who first apostatized from God, along with their chief the devil, who enviously deceived the first man under the form of a serpent. But the same holy Scripture affords the most ample testimony that even godly men have been called angels; for of John it is written: “Behold, I send my messenger (angel) before Your face, who shall prepare Your way.” [Mark 1:2] And the prophet Malachi, by a peculiar grace specially communicated to him, was called an angel [Malachi 2:7].

Let us omit, then, the fables of those scriptures which are called apocryphal, because their obscure origin was unknown to the fathers from whom the authority of the true Scriptures has been transmitted to us by a most certain and well-ascertained succession. For though there is some truth in these apocryphal writings, yet they contain so many false statements, that they have no canonical authority. We cannot deny that Enoch, the seventh from Adam, left some divine writings, for this is asserted by the Apostle Jude in his canonical epistle. But it is not without reason that these writings have no place in that canon of Scripture which was preserved in the temple of the Hebrew people by the diligence of successive priests; for their antiquity brought them under suspicion, and it was impossible to ascertain whether these were his genuine writings, and they were not brought forward as genuine by the persons who were found to have carefully preserved the canonical books by a successive transmission. So that the writings which are produced under his name, and which contain these fables about the giants, saying that their fathers were not men, are properly judged by prudent men to be not genuine; just as many writings are produced by heretics under the names both of other prophets, and more recently, under the names of the apostles, all of which, after careful examination, have been set apart from canonical authority under the title of Apocrypha. There is therefore no doubt that, according to the Hebrew and Christian canonical Scriptures, there were many giants before the deluge, and that these were citizens of the earthly society of men, and that the sons of God, who were according to the flesh the sons of Seth, sunk into this community when they forsook righteousness. Nor need we wonder that giants should be born even from these. For all of their children were not giants; but there were more then than in the remaining periods since the deluge. And it pleased the Creator to produce them, that it might thus be demonstrated that neither beauty, nor yet size and strength, are of much moment to the wise man, whose blessedness lies in spiritual and immortal blessings, in far better and more enduring gifts, in the good things that are the peculiar property of the good, and are not shared by good and bad alike. It is this which another prophet confirms when he says, “These were the giants, famous from the beginning, that were of so great stature, and so expert in war. Those did not the Lord choose, neither gave He the way of knowledge unto them; but they were destroyed because they had no wisdom, and perished through their own foolishness.” – Augustine, City of God, book 15, chapter 23