John Chrysostom

"Recompense to no man evil for evil." For if thou findest fault with another who plots against thee, why dost thou make thyself liable to this accusation? If he did amiss how comest thou 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."

Homily on Romans 22 ↗

Theophylact of Ohrid

If you reproach another for having done evil, then why do you imitate him and do evil yourself? He did not say: do not do evil to a believer, but: "to no one," whether he be a pagan or anyone else. He says this not so that we live for vainglory, but so that we do not give occasion to reproach us to those who desire it. For he requires that we live without causing offense and without stumbling, because many are watching us and what concerns us.

Commentary on Romans ↗

Cyprian

That evil is not to be returned for evil. In the Epistle of Paul to the Romans: "Rendering to no man evil for evil." Also in the same place: "Not to be overcome of evil, but overcome evil with good." Of this same thing in the Apocalypse: "And He said unto me, Seal not the words of the prophecy of this book; because now the time is at hand. …

Treatise XII Three Books of Testimonies Against the Jews ↗

Thomas Aquinas

Then when he says, to no man rendering evil for evil, he teaches what pertains to beneficence by excluding its contrary: first, he teaches not to do evil to another for revenge; second, he teaches not to do evil for the sake of defense, at revenge not yourselves. In regard to the first he does three things: first, he forbids revenge when he says: to no man rendering evil for evil: if I have returned evil for evil (Ps 7:5); do not repay evil with evil (1 Pet 3:9). …

Commentary on Romans ↗