Exodus 7:3; Exodus 8:15; Exodus 8:32

But rI will harden Pharaoh's heart, and though I smultiply my signs and wonders in the land of Egypt,

15 But when Pharaoh saw that there was a yrespite, he zhardened his heart and would not listen to them, as the Lord had said.

32 But Pharaoh ohardened his heart this time also, and did not let the people go.