12 Yet Yahweh made the heart of Pharaoh steadfast, so that he did not hearken to them just as Yahweh had spoken to Moses.
Exodus 9:12 Cross References - CLV
Exodus 4:21
21 And Yahweh said to Moses: When you go to return to Egypt, see to all the miracles which I place in your hand, that you do them before Pharaoh. Yet I shall make his heart steadfast, and he shall not dismiss the people.