Be ye not unequally yoked together with unbelievers: for what fellowship hath righteousness with unrighteousness? and what communion hath light with darkness? Wherefore come out from among them, and be ye separate, saith the Lord, and touch not the unclean thing; and I will receive you. 2 Corinthians 6:14, 17

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.Barnabas (A.D. 70-130) ch.4

Let us be imitators also of them which went about in goatskins and sheepskins, preaching the coming of Christ. Clement of Rome (A.D. 96) ch.17

Let us rather give offence to foolish and senseless men who exalt themselves and boast in the arrogance of their words, than to God.Clement of Rome (A.D. 96) ch. 21

Wherefore, brethren, let us forsake our sojourn in this world and do the will of Him that called us, and let us not be afraid to depart out of this world. Second Clement (A.D. 100) ch.5

And you know, brethren, that the sojourn of this flesh in this world is mean and for a short time, but the promise of Christ is great and marvelous, even the rest of the kingdom that shall be and of life eternal. What then can we do to obtain them, but walk in holiness and righteousness, and consider these worldly things as alien to us, and not desire them? For when we desire to obtain these things we fall away from the righteous path. Second Clement (A.D. 100) ch.5

But the Lord said, No servant can serve two masters. If we desire to serve both God and mammon, it is unprofitable for us: For what advantage is it, if a man gain the whole world and forfeit his soul? Now this age and the future are two enemies. The one speaks of adultery and defilement and avarice and deceit, but the other bids farewell to these. We cannot therefore be friends of the two, but must bid farewell to the one and hold companionship with the other. Second Clement (A.D. 100) ch.6

And I too, taking part in the festivity, am permitted by letter to bear you company and to rejoice with you, that you set not your love on anything after the common life of men, but only on God.Ignatius: to the Ephesians (A.D. 35-105) ch.9

The work is not of persuasiveness, but Christianity is at it’s greatest, whenever it is hated by the world. Ignatius: to the Romans (A.D. 35-105) ch.3

Bear with me, brethren. Do not hinder me from living; do not desire my death. Bestow not on the world one who desires to be God’s, neither allure him with material things. Suffer me to receive the pure light. When I am come thither, then shall I be a man. Ignatius: to the Romans (A.D. 35-105) ch.6

Rather stand you on my side, that is on God’s side. Speak not of Jesus Christ and withal desire the world. Ignatius: to the Romans (A.D. 35-105) ch.7

Since I see, that you are exceedingly anxious to understand the religion of the Christians, as to what God they trust and how they worship Him, that they all disregard the world and despise death.Letter to Diognetus (A.D. 125-200) ch. 1

Those who have never investigated concerning the truth, nor enquired concerning the deity, but have merely believed, and have been mixed up in business affairs and riches and heathen friendships, and many other affairs of this world – as many, I say, as devote themselves to these things, comprehend not the parables of the deity; for they are darkened by these actions, and are corrupted and become barren. Hermas (A.D. 150) Ante-Nicene Fathers vol.1 pg. 26

These are men who have been believers, but grew rich and became renowned among the Gentiles. They clothed themselves with great pride and became high-minded, and abandoned the truth and did not cleave to the righteous, but lived together after the manner of the Gentiles… Others at the last living with the Gentiles, and being corrupted by the vain opinions of the Gentiles, departed from God, and worked the works of the Gentiles. These therefore were numbered with the Gentiles. Hermas (A.D. 150) Ante-Nicene Fathers vol.1 pg.42

The Lord said: “Judge not, that you be not judged: for with what judgment you shall judge, you shall be judged.” [The meaning is] not certainly that we should not find fault with sinners, nor that we should consent to those who act wickedly; but that we should not pronounce an unfair judgment on the dispensations of God, inasmuch as He has Himself made provision that all things shall turn out for good, in a way consistent with justice. Irenaeus (A.D. 180) Ante-Nicene Fathers vol.1 pg.504

I do not wish to be a king; I am not anxious to be rich; I decline military command; I detest fornication; I am not impelled by an insatiable love of gain to go to sea; I do not contend for chaplets; I am free from a mad thirst for fame; I despise death… Die to the world, repudiating the madness that is in it. Live to God, and by apprehending Him lay aside your old nature. We were not created to die, but we die by our own fault. Our free-will has destroyed us; we who were free have become slaves; we have been sold through sin. Nothing evil has been created by God; we ourselves have manifested wickedness; but we, who have manifested it, are able again to reject it. Tatian (A.D.160) Ante-Nicene Fathers vol.2 pg.69

Among us nothing is ever said, or seen, or heard, which has anything in common with the madness of the circus, the immodesty of the theatre, the atrocities of the arena, the useless exercises of the wrestling-ground. Why do you take offence at us because we differ from you in regard to your pleasures? If we will not partake of your enjoyments, the loss is ours, if there be loss in the case, not yours. We reject what pleases you. Tertullian (A.D. 198) Ante-Nicene Fathers vol.3 pg. 46

We cannot sit down in fellowship with them, as neither can they with us. Things in this matter go by their turns. Now they have gladness and we are troubled. “The world,” says Jesus, “shall rejoice; you shall be sorrowful.” Let us mourn, then, while the heathen are merry, that in the day of their sorrow we may rejoice; lest, sharing now in their gladness, we share then also in their grief. You are too dainty, Christian, if you wouldst have pleasure in this life as well as in the next; nay, a fool you are, if you think this life’s pleasures to be really pleasures. Tertullian (A.D. 198) Ante-Nicene Fathers vol.3 pg. 90