Exodus 4:2-5, 17

So the LORD said to him, “What is that in your hand?” He said, “A rod.” And He said, “Cast it on the ground.” So he cast it on the ground, and it became a serpent; and Moses fled from it. Then the LORD said to Moses, “Reach out your hand and take it by the tail” (and he reached out his hand and caught it, and it became a rod in his hand), “that they may believe that the LORD God of their fathers, the God of Abraham, the God of Isaac, and the God of Jacob, has appeared to you.”

And you shall take this rod in your hand, with which you shall do the signs.”