Exodus 7:14-16

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

15Go to Pharaoh in the morning, when he goes out to the water, and you shall stand by the river’s bank to meet him; and the rod which was turned to a serpent you shall take in your hand.

16And you shall say to him, ‘The Lord God of the Hebrews has sent me to you, saying, “Let My people go, that they may serve Me in the wilderness”; but indeed, until now you would not hear!