There are two main ways the early church fathers went about arguing for non-violence. The first was that violence in general was wrong. You will see many quotes which condemn all sorts of violence or positions that use violence. The second approach was to condemn any conflict of interest in regard to lordship. If you had to make a pledge of loyalty to a state or acted in any manner which contradicted Christ (through worship of the gods, violence, or other evil), that was a problem. I think the early fathers would be pretty appalled with the extent that some of our patriotism goes, verging not only on nationalism, but worship of the state. While I focus mostly on quotes in regard to violence, you will see that this other notion threads its way in very frequently.
Regardless of which two views you take on defending pacifism in the early church, one view you won't find defended is that of killing another human being - for any reason. The video clip below provides a brief summary of this background (full video here), while I will put many of the quotes below. In essence, prior to 311 and Constantine's Edict of Milan, which made Christianity acceptable and more in tandem with the state, it is near impossible to find any orthodox Christian quote defending any sort of killing. Whether it was abortion, infanticide, military service, self-defense, or even capital punishment, Christians abhorred all killing and saw it as out of step with being a disciple of Christ.
As many as were called by grace, and displayed the first zeal, having cast aside their military girdles, but afterwards returned, like dogs, to their own vomit, (so that some spent money and by means of gifts regained their military stations); let these, after they have passed the space of three years as hearers, be for ten years prostrators. But in all these cases it is necessary to examine well into their purpose and what their repentance appears to be like. For as many as give evidence of their conversions by deeds, and not pretence, with fear, and tears, and perseverance, and good works, when they have fulfilled their appointed time as hearers, may properly communicate in prayers; and after that the bishop may determine yet more favourably concerning them. But those who take [the matter] with indifference, and who think the form of [not] entering the Church is sufficient for their conversion, must fulfil the whole time.
One who is a gladiator or teaches gladiators or swordsmanship or military skills or weapons training should stop or be excluded. . . . A soldier in the sovereign’s army[ 186] should not kill, or if he is ordered to kill, he should refuse. If he stops, so be it; otherwise he should be excluded. Concerning those who wear red[ 188] or believers who become soldiers or astrologers or magicians or such like: let them be excluded. One who has the power of the sword or the head of a city and wears red, let him stop or be excluded. A catechumen or a believer, if they want to be soldiers, let them be excluded because they distance themselves from God. (From "The Early Church on Killing")
Whoever has received the authority to kill, or else a soldier, they are not to kill in any case, even if they receive the order to kill. They are not to pronounce a bad word. Those who have received an honor are not to wear wreaths on their heads. Whosoever is raised to the authority of a prefect or the magistracy and does not put on the righteousness of the gospel is to be excluded from the flock and the bishop is not to pray with him. (FROM "THE EARLY CHURCH ON KILLING")
If anyone be a soldier or in authority, let him be taught not to oppress or to kill or to rob, or to be angry or to rage and afflict anyone. But let those rations suffice him which are given to him. But if they wish to be baptized in the Lord, let them cease from military service or from the [post of] authority, and if not let them not be received. Let a catechumen or a believer of the people, if he desire to be a soldier, either cease from his intention, or if not let him be rejected. For he hath despised God by his thought, and leaving the things of the Spirit, he hath perfected himself in the flesh and hath treated the faith with contempt.
This is the way of life: first, thou shalt love the God who made thee, secondly, thy neighbor as thyself: and all things whatsoever thou wouldest not should happen to thee, do not thou to another. The teaching of these words is this: Bless those who curse you, and pray for your enemies, and fast on behalf of those who persecute you: for what thanks will be due to you, if ye love only those who love you? Do not the Gentiles also do the same? But love ye those who hate you, and ye shall not have an enemy.
Concerning those who throw down their arms in time of peace, we have decreed that they should be kept from communion.
Hitherto I have served you as a soldier; allow me now to become a soldier to God. Let the man who is to serve you receive your donative. I am a soldier of Christ; it is not permissible for me to fight.
The professions and trades of those who are going to be accepted into the community must be examined. The nature and type of each must be established… brothel, sculptors of idols, charioteer, athlete, gladiator…give it up or be rejected. A military constable must be forbidden to kill, neither may he swear; if he is not willing to follow these instructions, he must be rejected. A proconsul or magistrate who wears the purple and governs by the sword shall give it up or be rejected. Anyone taking or already baptized who wants to become a soldier shall be sent away, for he has despised God.
(from "Church Order in the Apostolic Tradition" in The Early Christians in Their Own Words)
No Christian should go and become a soldier unless a Commander who has a sword compels him; let him not draw any guilt of blood shed upon himself.
For when God forbids us to kill, he not only prohibits us from open violence, which is not even allowed by the public laws, but he warns us against the commission of those beings which are esteemed lawful among men….Therefore, with regard to this precept of God, there ought to be no exception at all, but that it is always unlawful to put to death a man, whom God willed to be a sacred animal. (From "The Sacred Writings of Lactanitus" annotated edition)
If anyone should be so shameless as to inflict injury on a good and just man, such a man must bear it with calmness and moderation. He will not take upon himself his revenge. Rather, he will reserve it for the judgment of God. He must maintain innocence at all times and in all places. And this commandment is not limited to merely his not [being the first to] inflict injury on another. Rather, he should not even avenge it when injury is inflicted on him. For there sits on the judgment-seat a very great and impartial Judge. (FROM "THE SACRED WRITINGS OF LACTANITUS" ANNOTATED EDITION)
Religion is to be defended— not by putting to death— but by dying. Not by cruelty, but by patient endurance. Not by guilt, but by good faith. For the former belongs to evil, but the latter to the good. . . . For if you wish to defend religion by bloodshed, tortures, and guilt, it will no longer be defended. Rather, it will be polluted and profaned. . . . And, therefore, when we suffer such impious things, we do not resist even in word. Rather, we leave vengeance to God. We do not act as those persons who would have it appear that they are defenders of their gods, who rage without restraint against those who do not worship them. When provoked by injury, if he returns violence to his assailant, he is defeated. (From "Ante-Nicene Fathers," Vol. VII)
In what respect, then, does the wise and good man differ from the evil and foolish one? Is it not that he has unconquerable patience, of which the foolish are destitute? Is it not that he knows how to govern himself and to mitigate his anger— which those are unable to curb because they are without virtue? . . . What if a man gives way to grief and anger and indulges these emotions (which he should struggle against)? What if he rushes wherever injustice will call him? Such a man does not fulfill the duty of virtue. For he who tries to return an injury desires to imitate that very person by whom he has been injured. In short, he who imitates a bad man cannot be good. (From "A Dictionary of Early Christian Beliefs; A Reference Guide to More Than 700 Topics Discussed by the Early Church Fathers" edited by David W. Bercot)
Why do contests, fights, and contentions arise among men? Is it because impatience against injustice often excites great tempests? However, if you meet injustice with patience, then no virtue can be found more true. . . . In contrast, if injustice . . . has met with impatience on the same level as itself, . . . it will ignite a great fire that no stream can extinguish, but only the shedding of blood. (FROM "A DICTIONARY OF EARLY CHRISTIAN BELIEFS; A REFERENCE GUIDE TO MORE THAN 700 TOPICS DISCUSSED BY THE EARLY CHURCH FATHERS" EDITED BY DAVID W. BERCOT)
For what war should we not be fit and eager, even though unequal in numbers, we who are so willing to be slaughtered—if, according to that discipline of ours, it was not more lawful to be slain than to slay? (FROM "ANTI-NICENE FATHERS" )
But now inquiry is made about this point, whether a believer may turn himself unto military service, and whether the military may be admitted unto the faith, even the rank and file, or each inferior grade, to whom there is no necessity for taking part in sacrifices or capital punishments. There is no agreement between the divine and the human sacrament, the standard of Christ and the standard of the devil, the camp of light and the camp of darkness. One soul cannot be due to two masters--God and Caesar. And yet Moses carried a rod, and Aaron wore a buckle, and John (Baptist) is girt with leather and Joshua the son of Nun leads a line of march; and the People warred: if it pleases you to sport with the subject. But how will a Christian man war, nay, how will he serve even in peace, without a sword, which the Lord has taken away? For albeit soldiers had come unto John, and had received the formula of their rule; albeit, likewise, a centurion had believed; still the Lord afterward, in disarming Peter, unbelted every soldier. No dress is lawful among us, if assigned to any unlawful action. (From "Themelios" Volume 33, Issue 1)
To begin with the real ground of the military crown, I think we must first inquire whether warfare is proper at all for Christians. What sense is there in discussing the merely accidental, when that on which it rests is to be condemned? Do we believe it lawful for a human oathto be superadded to one divine, for a man to come under promise to another master after Christ?... Shall it be held lawful to make an occupation of the sword, when the Lord proclaims that he who uses the sword shall perish by the sword? And shall the son of peace take part in the battle when it does not become him even to sue at law?... Indeed, if, putting my strength to the question, I banish from us the military life…(FROM "ANTE-NICENE FATHERS" VOL.3)
If we are commanded, then, to love our enemies, as I have remarked above, whom have we to hate? If injured, we are forbidden to retaliate, lest we become as bad ourselves: who can suffer injury at our hands? ( From "Ante-Nicene Fathers" vol.3 pg. 45 )
If one attempt to provoke you by manual violence, the monition of the Lord is at hand: “To him,” He saith, “who smiteth thee on the face, turn the other cheek likewise.” Let outrageousness be wearied out by your patience. Whatever that blow may be, conjoined with pain and contumely, it shall receive a heavier one from the Lord. You wound that outrageous one more by enduring: for he will be beaten by Him for whose sake you endure. ( From "Ante-Nicene Fathers" vol.3 pg. 45)
No one gives the name of sheep to those who fall in battle with arms in hand, and while repelling force with force, but only to those who are slain, yielding themselves up in their own place of duty and with patience, rather than fighting in self-defense. ( From "Ante-Nicene Fathers" vol.3 pg. 415 )
Christ, in disarming Peter, disarmed every soldier. (FROM "ANTE-NICENE FATHERS" VOL.3)
The Christian does not hurt even his enemy. (fROM Tertullian Collection by Aeterna Press)
Only without the sword can the Christian wage war: the Lord has abolished the sword. (From "The Unfinished Conversation.")
Shall it be held lawful to make an occupation of the sword, when the Lord proclaims that he who uses the sword shall perish by the sword? And shall the son of peace take part in the battle when it does not become him even to sue at law? (FROM "ANTE-NICENE FATHERS" VOL.3)
Shall we carry a flag? It is a rival to Christ.
What man of sound mind, therefore, will affirm, while such is our character, that we are murderers? For we cannot eat human flesh till we have killed some one. The former charge, therefore, being false, if any one should ask them in regard to the second, whether they have seen what they assert, not one of them would be so barefaced as to say that he had. And yet we have slaves, some more and some fewer, by whom we could not help being seen; but even of these, not one has been found to invent even such things against us. For when they know that we cannot endure even to see a man put to death, though justly; who of them can accuse us of murder or cannibalism? Who does not reckon among the things of greatest interest the contests of gladiators and wild beasts, especially those which are given by you? But we, deeming that to see a man put to death is much the same as killing him, have abjured such spectacles. How, then, when we do not even look on, lest we should contract guilt and pollution, can we put people to death? And when we say that those women who use drugs to bring on abortion commit murder, and will have to give an account to God for the abortion, on what principle should we commit murder? For it does not belong to the same person to regard the very fœtus in the womb as a created being, and therefore an object of God’s care, and when it has passed into life, to kill it; and not to expose an infant, because those who expose them are chargeable with child-murder, and on the other hand, when it has been reared to destroy it. But we are in all things always alike and the same, submitting ourselves to reason, and not ruling over it. ( FROM "ANTE-NICENE FATHERS" VOL. 2)
for we have learned, not only not to return blow for blow,
nor to go to law with those who plunder and rob us, but to those who smite us onone side of the face to offer the other side also, and to those who take away our coat to give likewise our cloak
I do not think that a Christian ought to save his own life by the death of another; just as when he meets an armed robber he cannot return his blows, lest in defending his life he should stain his love toward his neighbor.” (Froom "Fight: A Christian Case for Non-Violence")
The soldiers of Christ require neither arms nor spears of iron. (FROM THE POLITICS OF LOVE: THE NEW TESTAMENT AND NON-VIOLENT REVOLUTION)
The servants of God do not rely for their protection on material defenses but on the divine Providence. (From The Politics of Love: The New Testament and Non-violent Revolution)
Why do you want to know my name? It is not permitted to me to serve in the military since I am a Christian. I cannot serve in the military; I cannot do wrong; I am a Christian. I will not do it; I cannot serve in the military. I will not serve; cut off my head; I do not serve the world, but I do serve my God.
I serve Jesus Christ the eternal King. I will no longer serve your emperors…It is not right for a Christian to serve the armies of this world. (From "Jesus for President")
I do not wish to be a king; I am not anxious to be rich; I decline military command… Die to the world, repudiating the madness that is in it. (From "Anti-Nicene Fathers" Vol. 2)
If a revolt had been the cause of the Christians existing as a separate group, the lawgiver of the Christians would not have forbidden entirely the taking of human life. He taught that it was never right for his disciples to go so far against a man, even if he should be very wicked; for he did not consider it compatible with his inspired legislation to allow the taking of human life in any form at all. Moreover, if Christians had originated from a revolt, they would not have submitted to laws that were so gentle which caused them to be killed as sheep and made then unable even to defend themselves against their persecutors. (From "Christian Ethics: A Very Short Introduction")
You cannot demand military service of Christians any more than you can of priests. We do not go forth as soldiers with the Emperor even if he demands this. (From "Against Celsus" VIII.68,73)
The more pious a man is, the more effective he is in helping the emperors—more so than the soldiers who go out into the lines and kill all the enemy troops that they can …. We who by our prayers destroy all daemons which stir up wars, violate oaths, and disturb the peace, are of more help to the emperors than those who seem to be doing the fighting …. And though we do not become fellow-soldiers with [the emperor], even if he presses for this, yet we are fighting for him and composing a special army of piety through our intercessions to God. (From "Against Celsus" 8.73)
To those who ask us whence we have come or whom we have for a leader, we say that we have come in accordance with the counsels of Jesus to cut down our warlike and arrogant swords of argument into ploughshares, and we convert into sickles the spears we formerly used in fighting. For we no longer take ‘sword against a nation,’ nor do we learn ‘any more to make war,’ having become sons of peace for the sake of Jesus, who is our leader, instead of following the ancestral customs in which we were strangers to the covenants. (From "The RIght Church: Live Like the First Christians")
…for neither Celsus nor they who think with him are able to point out any act on the part of Christians which savours of rebellion. And yet, if a revolt had led to the formation of the Christian commonwealth, so that it derived its existence in this way from that of the Jews, who were permitted to take up arms in defense of the members of their families, and to slay their enemies, the Christian Lawgiver would not have altogether forbidden the putting of men to death; and yet He nowhere teaches that it is right for His own disciples to offer violence to any one, however wicked. (From "The Sacred Writings of Origen")
And when the Spirit of prophecy speaks as predicting things that are to come to pass, He speaks in this way: “For out of Zion shall go forth the law, and the word of the Lord from Jerusalem. And He shall judge among the nations, and shall rebuke many people; and they shall beat their swords into ploughshares, and their spears into pruning-hooks: nation shall not lift up sword against nation, neither shall they learn war any more.” And that it did so come to pass, we can convince you. For from Jerusalem there went out into the world, men, twelve in number, and these illiterate, of no ability in speaking: but by the power of God they proclaimed to every race of men that they were sent by Christ to teach to all the word of God; and we who formerly used to murder one another do not only now refrain from making war upon our enemies, but also, that we may not lie nor deceive our examiners, willingly die confessing Christ. For that saying, “The tongue has sworn but the mind is unsworn,” might be imitated by us in this matter. But if the soldiers enrolled by you, and who have taken the military oath, prefer their allegiance to their own life, and parents, and country, and all kindred, though you can offer them nothing incorruptible, it were verily ridiculous if we, who earnestly long for incorruption, should not endure all things, in order to obtain what we desire from Him who is able to grant it. (From First Apology 39)
“We ourselves were well conversant with war, murder, and everything evil, but all of us throughout the whole wide earth have traded in our weapons of war. We have exchanged our swords for ploughshares, our spears for farm tools. Now we cultivate the fear of God, justice, kindness to men, faith, and the expectation of the future given to us by the Father himself through the Crucified One.”
(From "Dialogue with Trypho" 110.3.4 )
And we who were filled with war, and mutual slaughter, and every wickedness, have each through the whole earth changed our warlike weapons, – our swords into ploughs, and our spears into implements of tillage, – and we cultivate piety, righteousness, philanthropy, faith, and hope, which we have from the Father Himself through Him who was crucified. (From "Dialogue with Trypho" 50)
We who formerly treasured money and possessions more than anything else now hand over everything we have to a treasury for all and share it with everyone who needs it. We who formerly hated and murdered one another now live together and share the same table. We pray for our enemies and try to win those who hate us.
God called Abraham and commanded him to go out from the country where he was living. With this call God has roused us all, and now we have left the state. We have renounced all the things the world offers…. The gods of the nations are demons.
None of us offers resistance when he is seized, or avenges himself for your unjust violence, although our people are numerous and plentiful…it is not lawful for us to hate, and so we please God more when we render no requital for injury…we repay your hatred with kindness. ( From "Ante-Nicene Fathers" vol. 5 pg. 462)
Wars are scattered all over the earth with the bloody horror of camps. The whole world is wet with mutual blood. And murder–which is admitted to be a crime in the case of an individual–is called a virtue when it is committed wholesale. Impunity is claimed for the wicked deeds, not because they are guiltless, but because the cruelty is perpetrated on a grand scale. (From "The Sacred Writings of Saint Cyprian")
We, a numerous band of men as we are, have learned from His teaching and His laws that evil ought not to be requited with evil, that it is better to suffer wrong than to inflict it, that we should rather shed our own blood than stain our hands and our conscience with that of another. (From "Anti-Nicene Fathers" Vol. 6)
We would rather shed our own blood than stain our hands and our conscience with that of another. As a result, an ungrateful world is now enjoying–and for a long period has enjoyed–a benefit from Christ. For by his means, the rage of savage ferocity has been softened and has begun to withhold hostile hands from the blood of a fellow creature. In fact, if all men without exception…would lend an ear for a while to his salutary and peaceful rules,…the whole world would be living in the most peaceful tranquility. The world would have turned the use of steel into more peaceful uses and would unite together in blessed harmony. (From "Anti-Nicene Fathers" Vol. 6)
I summoned those who among us go by the name of Christians
. And having made inquiry, I discovered a great number and vast host of them, and raged against them, which was by no means becoming; for afterwards I learned their power.Wherefore
they began the battle, not by preparing weapons,nor arms, nor bugles; for such preparation is hateful to them,
on account of the God they bear about in their conscience. (From "The Sacred Writings of Justin Martyr")
Those soldiers were filled with wonder and admiration at the grandeur of the man’s piety and generosity and were struck with amazement. They felt the force of this example of pity. As a result, many of them were added to the faith of our Lord Jesus Christ and threw off the belt of military service. (From "Anti-Nicene Fathers" Vol. 6)
Do no one any injury at any time; provoke no one to anger. If an injury is done to you, look to Jesus Christ. And even as you desire Him to forgive your transgressions, also forgive others theirs. (From "Ante-Nicene Fathers" vol. 6 pg. 161)
Nor an eye for an eye and a tooth for a tooth, for him who counts no man his enemy, but all his neighbors, and therefore can never stretch out his hand for vengeance. ("Proof of the Apostolic Preaching" 96)
Nothing is more precious than peace, by which all war, both in heaven and earth, is brought to an end. Therefore have need of meekness, by which the prince of this world is brought to nought. (From Epistle to the Trallians 4)
For we are not to delineate the faces of idols, we who are prohibited to cleave to them; nor a sword, nor a bow, following as we do, peace. (From "Anti-Nicene Fathers" Vol. 2)
The Christian poor are “an army without weapons, without war, without bloodshed, without anger, without defilement.
Above all Christians are not allowed to correct by violence sinful wrongdoings.
We Christians are a peaceful race…for it is not in war, but in peace, that we are trained.
If you enroll as one of God’s people, then heaven is your country and God your lawgiver.
Do not willingly use force and do not return force when it is used against you. (From "The Sacred Writings of Commodianus")
Christians, instead of arming themselves with swords, extend their hands in prayer. (From "On the Incarnation of the Word")
Say to those that hate and curse you, You are our brothers!
It is the Christians, O Emperor, who have sought and found the truth, for they acknowledge God…. They show love to their neighbors. They do not do to another what they would not wish to have done to themselves. They speak gently to those who oppress them, and in this way they make them their friends. It has become their passion to do good to their enemies…. This, O Emperor, is the rule of life of the Christians, and this is their manner of life.
Christians appeal to those who wrong them and make them friendly to themselves; they are eager to do good to their enemies; they are mild and conciliatory.
I am a Christian. He who answers thus has declared everything at once—his country, profession, family; the believer belongs to no city on earth but to the heavenly Jerusalem.
I recognize no empire of this present age.
Chapter VII: ...This [messenger] He sent to them. Was it then, as one might conceive, for the purpose of exercising tyranny, or of inspiring fear and terror? By no means, but under the influence of clemency and meekness. As a king sends his son, who is also a king, so sent He Him; as God He sent Him; as to men He sent Him; as a Saviour He sent Him, and as seeking to persuade, not to compel us; for violence has no place in the character of God...
Chapter V: ...As citizens, they share in all things with others, and yet endure all things as if foreigners. Every foreign land is to them as their native country, and every land of their birth as a land of strangers. They marry, as do all [others]; they beget children; but they do not destroy their offspring. They have a common table, but not a common bed. They are in the flesh, but they do not live after the flesh. They pass their days on earth, but they are citizens of heaven. They obey the prescribed laws, and at the same time surpass the laws by their lives. They love all men, and are persecuted by all. They are unknown and condemned; they are put to death, and restored to life. They are poor, yet make many rich; they are in lack of all things, and yet abound in all; they are dishonoured, and yet in their very dishonour are glorified. They are evil spoken of, and yet are justified; they are reviled, and bless; they are insulted, and repay the insult with honour; they do good, yet are punished as evil-doers. When punished, they rejoice as if quickened into life; they are assailed by the Jews as foreigners, and are persecuted by the Greeks; yet those who hate them are unable to assign any reason for their hatred.