103 Do you then forgive injuries done to you that you may be children of Jacob. Be not provoked as was Esau. Imitate holy David, who as a good master left us what we should follow, saying: “Instead of loving me they spoke against me, but I prayed,” and when he was reviled, he prayed. Prayer is a good shield, wherewith contumely is kept away, cursing is repelled and often is turned back on those who utter it, so that they are wounded by their own weapons. “Let them curse,” he says, “but bless You.” The curse of man is to be sought for, which procures the blessing of the Lord.
Source: Letters (New Advent)