Exodus 7:14-16

14Then the Lord said to Moses, ‘Pharaoh's mind is still hard. He refuses to let the people go.

15Go to Pharaoh in the morning when he goes to the river. Wait for him by the edge of the river. Then take in your hand the stick that became a snake.

16Then say to Pharaoh, “The Lord, the God of the Israelites, has sent me to you to say, ‘Let my people go, so that they may worship me in the desert.’ But until now, you have not listened to my message.