Gregory the Dialogist

27. Correctable sins are indeed borne, because after they depart from the will of the one who committed them, they can be wholesomely purged through satisfaction. But the sins of those in whose minds they have become ingrained through impenitence are not borne. Whence John also says: "There is a sin unto death; I do not say that one should pray for that" (1 John 5:16). A sin unto death is that which is committed by one who can never come to his senses. …

Commentary on 1 Kings, Book 6, Chapter 2 ↗