1 Corinthians 16:24
Thirdly, the speaker too himself will both incur the bad opinion of the hearer, and will provoke God to more anger against himself.
Wherefore, I beseech you, let us cast from us every word that is unsavory. If there be any thing good unto edification, this let us speak.
But have you a fancy to avenge yourself on the other person? Why then punish yourself instead of him? Nay, do thou, who art so earnestly seeking redress from those who have annoyed you, avenge yourself as Paul recommended to take vengeance. “If your enemy hunger, feed him; if he thirst, give him drink.” But if you do not so, but only plot against him, you point the sword against yourself.
Wherefore if that other speak evil, answer him with praises and commendations. For so will you be able both to take vengeance on him, and wilt deliver yourself from evil surmising. Since he that feels pain at hearing ill of himself, is thought to be so affected because of some consciousness of evil: but he that laughs to scorn what is said, exhibits a most unquestionable token of his not being conscious to himself of any evil thing.
Seeing then that you profit neither your hearer, nor yourself, nor him that is accused, and dost but point your sword at your own self, even from such considerations do thou learn more soberness. For one ought indeed to be moved by the thought of the kingdom of heaven, and of what pleases God: but since you are of grosser disposition and bitest like a wild beast, hereby even be thou instructed; that these arguments having corrected you, you may be able to order yourself simply from consideration of what pleases God; and having come to be above every passion, may obtain the heavenly blessings:— which may God grant us all to obtain, through the grace of our Lord Jesus Christ, and His mercy towards mankind; with Whom, to the Father and the Holy Spirit, be glory, power, honor, now and henceforth, and unto everlasting ages. Amen.
Source: Homilies on First Corinthians (New Advent)