Exodus 7:10-15

10So Moses and Aaron went to Pharaoh and did just as the Lord commanded. Aaron threw his staff down in front of Pharaoh and his officials, and it became a snake. 11Pharaoh then summoned wise men and sorcerers, and the Egyptian magicians also did the same things by their secret arts: 12Each one threw down his staff and it became a snake. But Aaron’s staff swallowed up their staffs. 13Yet Pharaoh’s heart became hard and he would not listen to them, just as the Lord had said. 14Then the Lord said to Moses, “Pharaoh’s heart is unyielding; he refuses to let the people go. 15Go to Pharaoh in the morning as he goes out to the river. Confront him on the bank of the Nile, and take in your hand the staff that was changed into a snake.