Exodus 9:12

12. And the Lord hardened the heart of Pharaoh That is, by sending this manifestation of his anger he made his heart more hard . Punishment always hardens if it does not soften . It is worthy of remark that now, for the first time in the history, it is said that “the Lord hardened,” although this result of his sin had been predicted, Exodus 4:21. Exodus 7:13; Exodus 7:13 is no exception; see the note . Here, then, is another marked stage in the history of these judgments . By persistent disobedience Pharaoh has now so blunted his moral sense that it is morally certain that he will not repent; that is, he has reached that state where punishment will only harden. Yet God punishes still. Since he will not honour him by obedience he must do it through punishment.