3 You have read in the Holy Psalms, how that he who speaks in them imprecates, as it would seem, many curses upon his enemies. And surely, one may say, he who speaks in the Psalms is a righteous man; wherefore then does he so wish evil upon his enemies? He does not wish, but he foresees, it is a prophecy of one who is telling things to come, not a vow of malediction; for the prophets knew by the Spirit to whom evil was appointed to happen, and to whom good; and by prophecy they spoke as if they wished for what they did foresee.
But how can you know whether he for whom today you are asking evil, may not tomorrow be a better man than yourself? But you will say, I know him to be a wicked man. Well: you must know that you are wicked too. Although it may be you take upon yourself to judge of another's heart what you do not know; but as for your own self you know that you are wicked. Do you not hear the Apostle saying, “Who was before a blasphemer, and a persecutor, and injurious: but I obtained mercy, because I did it ignorantly in unbelief?” Now when the Apostle Paul persecuted the Christians, binding them wherever he found them, and drew them to the Chief Priests to be questioned and punished, what think ye, brethren, did the Church pray against him, or for him?
Surely the Church of God which had learned instruction from her Lord, who said as He hung upon the Cross, “Father, forgive them, for they know not what they do,” so prayed for Paul (or rather as yet Saul), that that might be wrought in him which was wrought. For in that he says, “But I was unknown by face to the churches of Judæa which are in Christ: only they heard that he who persecuted us in times past, now preaches the faith which once he destroyed; and they magnified God in me;” why did they magnify God, but because they asked this of God, before it came to pass?
Source: Sermons on Selected Lessons of the New Testament (New Advent)