Do not long for division, but rather bring those who contend to peace. Judge righteously, and do not respect persons in reproving for transgressions. You shall not be undecided whether or not it shall be. Didache (A.D. 80-140) ch. 4
Every kind of faction and schism was abominable in your sight. You mourned over the transgressions of your neighbors: their deficiencies you deemed your own. Clement of Rome (A.D. 96) ch. 2
Every kind of honor and happiness was bestowed upon you, and then was fulfilled that which is written, “My beloved did eat and drink, and was enlarged and became fat, and kicked.” Hence flowed emulation and envy, strife and sedition, persecution and disorder, war and captivity. So the worthless rose up against the honored, those of no reputation against such as were renowned, the foolish against the wise, the young against those advanced in years. Clement of Rome (A.D. 96) ch. 3
Why are there strifes, and tumults, and divisions, and schisms, and wars among you? Have we not [all] one God and one Christ? Is there not one Spirit of grace poured out upon us? And have we not one calling in Christ? Why do we divide and tear to pieces the members of Christ, and raise up strife against our own body, and have reached such a height of madness as to forget that “we are members one of another?” Remember the words of our Lord Jesus Christ, how He said, “Woe to that man [by whom offences come]! It were better for him that he had never been born, than that he should cast a stumbling-block before one of my elect. Yea, it were better for him that a millstone should be hung about [his neck], and he should be sunk in the depths of the sea, than that he should cast a stumbling-block before one of my little ones. Your schism has subverted [the faith of] many, has discouraged many, has given rise to doubt in many, and has caused grief to us all. And still your sedition continues. Take up the epistle of the blessed Apostle Paul. What did he write to you at the time when the Gospel first began to be preached? Truly, under the inspiration of the Spirit, he wrote to you concerning himself, and Cephas, and Apollos, because even then parties had been formed among you. Clement of Rome (A.D. 96) ch. 46-47
Who therefore is noble among you? Who is compassionate? Who is fulfilled with love? Let him say; If by reason of me there be faction and strife and divisions, I retire, I depart, whither you will, and I do that which is ordered by the people: only let the flock of Christ be at peace with its duly appointed presbyters. Clement of Rome (A.D. 96) ch.54
As children therefore [of the light] of the truth, shun division and wrong doctrines; and where the shepherd is, there follow you as sheep. For many specious wolves with baneful delights lead captive the runners in God’s race; but, where you are at one, they will find no place. Ignatius: to the Philadelphians (A.D. 35-105) ch.2
Abstain from noxious herbs, which are not the husbandry of Jesus Christ, because they are not the planting of the Father. Not that I have found division among you, but filtering. Ignatius: to the Philadelphians (A.D. 35-105) ch.3
He shall also judge those who give rise to schisms, who are destitute of the love of God, and who look to their own special advantage rather than to the unity of the Church; and who for trifling reasons, or any kind of reason which occurs to them, cut in pieces and divide the great and glorious body of Christ, and so far as in them lies, [positively] destroy it,-men who prate of peace while they give rise to war, and do in truth strain out a gnat, but swallow a camel. Irenaeus (A.D. 180) Ante-Nicene Fathers vol.1 pg. 508