Exodus 4:2-5

So GOD said, “What’s that in your hand?” “A staff.” “Throw it on the ground.” He threw it. It became a snake; Moses jumped back—fast! GOD said to Moses, “Reach out and grab it by the tail.” He reached out and grabbed it—and he was holding his staff again. “That’s so they will trust that GOD appeared to you, the God of their fathers, the God of Abraham, the God of Isaac, and the God of Jacob.”