Exodus 7:9-10

“When Pharaoh speaks to you, saying, ‘Do a wonder for yourselves,’ you will say to Aaron, ‘Take your staff and throw it before Pharaoh, and it will become a snake.’ ” And Moses and Aaron came to Pharaoh, and they did so, as Yahweh had commanded. And Aaron threw his staff before Pharaoh and before his servants, and it became a snake.