But he did you some wrong, maybe, and injured you? Groan at it, and do not rail. Weep, not for the wrong done you, but for his perdition, as your Master also wept at Judas, not because Himself was to be crucified, but because he was a traitor. Has he insulted you and abused you? Beseech God for him, that He may speedily become appeased toward him. He is your brother, he is a member of you, the fruit of the same pangs as yourself, he has been invited to the same Table. But he only makes fresh assaults upon me, it may be said.
Then is your reward all the greater for this. On this ground then there is the best reason for abating one's anger, since it is a mortal wound that he has received, since the devil has wounded him. Do not thou then give a further blow, nor cast yourself down together with him. For so long as you stand you have the means of saving him also. But if you dash yourself down by insulting deeds in return, who is then to lift you both up? Will he that is wounded? Nay, for he cannot, now that he is down.
But will you that are fallen along with him? And how shall you, that couldest not support your own self, be able to lend a hand to another? Stand therefore now nobly, and setting your shield before you, and draw him, now he is dead, away from the battle by your long-suffering. Rage has wounded him, do not thou also wound him, but cast out even that first shaft. For if we associate with each other on such terms, we shall soon all of us become healthful. But if we arm ourselves against one another, there will be no farther need even of the devil to our ruin.
For all war is an evil, and civil war especially. But this is a sorer evil than even a civil one, as our mutual rights are greater than those of citizenship, yea, than of kindred itself. Of old, Abel's brother slew him and shed the blood of his kinsman. But this murder is more lawless than that, in that the rights of kinsmanship are greater, and the death a sorer evil. For he wounded the body, but you have whetted your sword against the soul. “But you first suffered ill.” Yes, but it is not suffering ill, but doing it, that is really suffering ill.
Now consider; Cain was the slayer, Abel was the slain. Who then was the dead? He that after death cries, (for He says, “The voice of your brother's blood cries to Me,”), or he who while he lived was yet trembling and in fear? He was, assuredly he was, more an object of pity than any dead man. Do you see how to be wronged is better, though a man come even to be murdered? Learn that to wrong is worse, though a man should be strong enough even to kill. He smote and cast down his brother, yet the latter was crowned, the former was punished.
Abel was made away with and slain wrongfully, but he even when dead accused, and convicted and overcame: the other, though alive, was speechless, and was ashamed, and was convicted, and effected the opposite of what he intended. For he made away with him because he saw him beloved, expecting to cast him out of the love also. Yet he did but make the love more intense, and God sought him more when dead, saying, “Where is your brother Abel?” For you have not extinguished the desire towards him by your envy, but hast kindled it up the more.
You have not lessened his honor by slaying him, but hast made it the more ample. Yet before this God had even made him subject to you, whereas since you have slain him, even when dead, he will take vengeance upon you. So great was my love towards him. Who then was the condemned person, the punisher or the punished? He that enjoyed so great honor from God, or he that was given up to a certain novel and unexpected punishment? You did not fear him (he would say) while alive, you shall fear him therefore when dead.
You did not tremble when on the point of thrusting with the sword. You shall be seized, now the blood is shed, with a continual trembling. While alive he was your servant, and you showed no forbearance to him. For this reason, now he is dead, he has become a master you shall be afraid of. Thinking then upon these things, beloved, let us flee from envy, let us extinguish malice, let us recompense one another with charity, that we may reap the blessings rising from it, both in the present life and the life which is to come, by the grace and love toward man, etc. Amen.
Source: Homilies on Romans (New Advent)