“Be not wise in your own conceits.” This is, do not think that you can do for yourselves. Because the Scripture says in another place besides, “Woe to them that are wise in their own eyes, and prudent in their own sight.” And by this again, he secretly draws off recklessness, and reduces conceit and turgidity. For there is nothing that so elates men and makes them feel different from other people, as the notion that they can do by themselves. Whence also God has placed us in need one of another, and though thou be wise you will be in need of another: but if you think that you are not in need of him, you will be the most foolish and feeble of men. For a man of this sort bares himself of all succor, and in whatever error he may run into, will not have the advantage either of correction or of pardon, and will provoke God by his recklessness, and will run into many errors. For it is the case, aye, and often too, that a wise man does not perceive what is needful, and a man of less shrewdness hits upon somewhat that is applicable. And this happened with Moses and his father-in-law, and with Saul and his servant, and with Isaac and Rebecca. Do not then suppose that you are lowered by needing another man. For this exalts you the more, this makes you the stronger, and the brighter too, and the more secure.
Ver. 17. “Recompense to no man evil for evil.”
For if you find fault with another who plots against you, why do you make yourself liable to this accusation? If he did amiss how do you come not to shun imitating him? And observe how he puts no difference here but lays down one law for all. For he does not say, “recompense not evil” to the believer, but to “no man,” be he heathen, be he contaminated, or what not. “Provide things honest in the sight of all men.”
Ver. 18. “If it be possible, as much as lies in you, live peaceably with all men.”
This is that: “let your light shine before men”, not that we are to live for vanity, but that we are not to give those who have a mind for it a handle against us. Whence he says also in another place, “Give none offense, neither to the Jews, nor to the Gentiles, nor to the Church of God.” And in what follows he limits his meaning well, by saying, “If it be possible.” For there are cases in which it is not possible, as, for instance, when we have to argue about religion, or to contend for those who are wronged. And why be surprised if this be not universally possible in the case of other persons, when even in the case of man and wife he broke through the rule? “But if the unbelieving depart, let him depart.” And his meaning is nearly as follows: Do your own part, and to none give occasion of war or fighting, neither to Jew nor Gentile. But if you see the cause of religion suffering anywhere, do not prize concord above truth, but make a noble stand even to death. And even then be not at war in soul, be not averse in temper, but fight with the things only. For this is the import of “as much as in you lies, be at peace with all men.” But if the other will not be at peace, do not thou fill your soul with tempest, but in mind be friendly (φίλος, several manuscripts φιλόσοφος) as I said before, without giving up the truth on any occasion.
Ver. 19. “Dearly beloved, avenge not yourselves, but rather give place unto wrath. For it is written, Vengeance is mine; I will repay, says the Lord.”
Unto what wrath? To the wrath of God. Now since what the injured man desires most to see is, himself having the pleasure of revenge, this very thing he gives him in full measure, that if you dost not avenge yourself, he means, God will be your avenger. Leave it then to Him to follow up your wrongs. For this is the force of “give place unto wrath.” Then to give further comfort, he brings the quotation forward also, and after winning him more throughly to himself in this way, he demands more Christian heroism (φιλοσόφιάν) of him, and says:
<!--<span class="stiki"></span>-->Ver. 20, 21. “If your enemy hunger, feed him; if he thirst, give him to drink; for in so doing you shall heap coals of fire upon his head. Be not overcome of evil, but overcome evil with good.”
Source: Homilies on Romans (New Advent)