Exodus 4:2-5

The LORD said to him, “What is that in your hand?” Moses answered, “It is my walking stick.” The LORD said, “Throw it on the ground.” So Moses threw it on the ground, and it became a snake. Moses ran from the snake, but the LORD said to him, “Reach out and grab the snake by its tail.” When Moses reached out and took hold of the snake, it again became a stick in his hand. The LORD said, “This is so that the Israelites will believe that the LORD appeared to you. I am the God of their ancestors, the God of Abraham, the God of Isaac, and the God of Jacob.”