Psalms 51:13

But see what he annexeth: "With Principal Spirit," he saith, "confirm Thou me." Wherein "confirm"? Because Thou hast pardoned me, because I am secure, that what Thou hast forgiven is not to be ascribed, on this being made secure and with this grace confirmed, therefore I am not ungrateful. But I shall do what? "I would teach unrighteous men Thy ways" (ver. 13). Being myself of the unrighteous (that is, one that was myself an unrighteous man, now no longer unrighteous; the Holy Spirit not having been taken away from me, and I being confirmed with Principal Spirit). "I would teach unrighteous men Thy ways." What ways wilt thou teach unrighteous men? "And ungodly men to Thee shall be converted." If David's sin is counted for ungodliness, let not ungodly men despair of themselves, forasmuch as God hath spared an ungodly man; but let them take heed that to Him they be converted, that His ways they learn. But if David's deed is not counted for ungodliness, but this is properly call ungodliness, namely, to apostatize from God, not to worship one God, or never to have worshipped, or to have forsaken, Him whom one did worship, then what he saith hath the force of superabundance, "And ungodly men shall to Thee be converted." So full art thou of the fatness of mercy, that for those converted to Thee, not only sinners of any sort, but even ungodly, there is no cause for despair. Wherefore? That believing on Him that justifieth an ungodly man, their faith may be counted for righteousness.

And what Christ worked in Paul, making him from a persecutor into a preacher, how much this may contribute to human salvation, let the Apostle himself speak that no one conscious of great sins may despair of God's mercy. Human speech, he says, is worthy of full acceptance, because Christ Jesus came into this world to save sinners, among whom I am the first. But for this reason, I received mercy, that in me first Christ Jesus might show all long-suffering, as a pattern for those who are going to believe in Him for eternal life. Who, then, being inspired by such a great example, could despair of salvation under the hand of the Almighty Physician, considering that he who once ravaged the faith he now preaches, not only escaped the punishment of the persecutor but also deserved the crown of the teacher, and whose blood he sought in his members to shed in his rage, he poured out his own blood in faith for His name? Therefore, Rome has the head of the nations, two lights of the nations kindled by Him who illuminates every man coming into this world: one, in which God elevated humble weakness; the other, in which He healed condemnable sin. In the one, let us learn not to boast; in the other, not to despair. How briefly the great examples set before us teach, how beneficial they are; which we should always remember, and in their praise magnify the true light. Therefore, let no one exalt himself in the lofty status of this world: Peter was a fisherman. Let no one flee from God's mercy by thinking of their own sinfulness: Paul was a persecutor. The former says: The Lord became a refuge for the poor; the latter says: I will teach the wicked Your ways, and sinners shall be converted to You.