Exodus 7:14-16

14Then the Lord said to Moses, “Pharaoh’s heart is hard; he refuses to let the people go.

15Go to Pharaoh in the morning as he is going out to the water, and wait for him on the bank of the Nile; and you shall take in your hand the staff that was turned into a serpent.

16You shall say to him, ‘The Lord, the God of the Hebrews, has sent me to you, saying, “Let My people go, so that they may serve Me in the wilderness. But behold, you have not listened until now.”