Exodus 7:3-6

And I will harden Pharaoh's heart, and multiply my signs and my wonders in the land of Egypt. But Pharaoh shall not hearken unto you, that I may lay my hand upon Egypt, and bring forth mine armies, and my people the children of Israel, out of the land of Egypt by great judgments. And the Egyptians shall know that I am the LORD, when I stretch forth mine hand upon Egypt, and bring out the children of Israel from among them. And Moses and Aaron did as the LORD commanded them, so did they.