Exodus 7:3-5

But I will make Pharaoh’s heart stubborn so I can multiply my miraculous signs and wonders in the land of Egypt.  Even then Pharaoh will refuse to listen to you. So I will bring down my fist on Egypt. Then I will rescue my forces—my people, the Israelites—from the land of Egypt with great acts of judgment.  When I raise my powerful hand and bring out the Israelites, the Egyptians will know that I am the L ord .” (Exodus 7:3-5 NLT)