Tertullian, Against Marcion 24

You are misreading repentance in God's case, as if He repented out of instability or improvidence, or simply because He remembers some sin — since He said, 'I repent that I made Saul king,' as though repentance always means confessing an evil deed or mistake. But it does not always work that way. Scripture itself shows repentance confessed even over good deeds, to the envy and reproach of the one who proved ungrateful for a benefit. Take Saul: the Creator, who had not sinned, announced His repentance about burdening Saul when He took him into the kingdom and increased him with the Holy Spirit — for he was still the best, as God said, 'There was not such a one among the sons of Israel,' and He had chosen him most worthily. Yet He was not ignorant of how it would turn out. No one will saddle God with improvidence, since you yourself confess Him to be God and provident; providence is the very property of His divinity. The evil deed of Saul, as I said, burdened God's repentance with a profession that — with no sin attaching to the choice of Saul — is to be understood as envious rather than criminal. (1 Samuel 15:35)

You object: 'But I see it as criminal in the case of the Ninevites, for Jonah says: "The Lord repented of the evil which He had said He would do to them, and He did not do it." And Jonah himself said to God: "Therefore I fled beforehand to Tarshish, because I knew you to be merciful and full of mercy, patient and very merciful, repenting of evils."' Well put — he led with the title of the best God, the most patient over the wicked and most abundant in mercy and pity toward those who acknowledge and lament their sins, like the Ninevites then. If that is what 'best' means, you should have stopped earlier: evil does not belong to such a one, that is, to the best. Even Marcion admits a good tree cannot produce evil fruit, yet he named an evil that the best cannot comprehend. Is there some interpretation of those evils that could also have occurred in the best? There is. We say that 'evil' here does not mean evil reduced to the Creator's nature, but evil assigned to His power as Judge — according to which He announced: 'I am He who creates evils,' and: 'Behold, I send evils upon you' — not sinful, but avenging. We have sufficiently cleared the infamy of such evils as befitting a Judge. Just as evils are spoken of a judge without reproach, nor do they make the judge evil by that name, so this 'evil' is to be understood as drawn from judicial evils and belonging to the Judge. Even among the Greeks, 'evils' sometimes means vexations and injuries, not malignities — just as in this passage. So if the Creator repented of His 'evil' as if it were a creature to be reproached and judged for sin, yet no admitted crime will be reckoned to the Creator, who justly and deservedly decreed the abolition of the most wicked city. What He justly destined, He destined not evilly but from justice, not from evil; He named the punishment itself 'evil' from the evil and merit of its suffering. (Jonah 3:10)

So you will say: if you excuse 'evil' as a name of justice because He justly destined destruction for the Ninevites, then He is also to be blamed for repenting of justice, which is not to be repented of. On the contrary, God does not repent of justice. It remains to acknowledge what God's repentance actually is. It is not that because a man repents from the memory of much sin, sometimes even from the ingratitude of some good work, God repents in the same way. Inasmuch as God neither admits evil nor condemns good, to that extent there is no place for repentance of good or evil with Him. The same Scripture determines this for you, when Samuel says to Saul: 'The Lord has torn the kingdom of Israel from your hand today and will give it to your neighbor, who is better than you, and Israel will be split in two, and it will not turn back nor repent, because He is not a man to repent.' This definition establishes a different form of divine repentance in all things — not reckoned from improvidence or levity or any condemnation of good or evil work, like human repentance. What then is the manner of divine repentance? It is now clear, if you do not refer it to human conditions. Nothing else is understood than a simple conversion of the prior sentence, which can be admitted without reproach even in a man, much less in God, whose every sentence lacks fault. Even in the Greek, the word for repentance is composed not from confession of sin but from change of mind — which we show happens with God because of the occurrence of changing things.