Exodus 4:21

4:21 The Lord said to Moses, “When you go back to Egypt, see that you do before Pharaoh all the wonders I have put under your control. But I will harden his heart and he will not let the people go.

Exodus 11:10

11:10 So Moses and Aaron did all these wonders before Pharaoh, but the Lord hardened Pharaoh’s heart, and he did not release the Israelites from his land.