To me belongs vengeance, and recompense; their foot shall slide in due time: for the day of their calamity is at hand, and the things that shall come upon them make haste.
All Commentaries on Deuteronomy 32:35 Go To Deuteronomy 32
Ambrose of Milan
AD 397
Since God said in the Old Testament, “Vengeance is mine, I shall repay,” he says in the Gospel that we should pray for those who harm us, in order that he who promised vengeance might not seek revenge against them. For [God] wants to forgive by your will, which is fitting according to his promise. But if you seek revenge, you have it, since the unjust man is punished more by his thoughts than by judicial severity.