Exodus 7:9-10

He said, “Pharaoh will say to you, ‘Do a miracle.’ When he does, speak to Aaron. Tell him, ‘Take your walking stick and throw it down in front of Pharaoh.’ It will turn into a snake.” So Moses and Aaron went to Pharaoh. They did exactly as the LORD had commanded them. Aaron threw the stick down in front of Pharaoh and his officials. It turned into a snake.