Exodus 4:2-5

2 The Lord said to him, "What is that in your hand?" He said, "A staff."
3 And he said, "Throw it on the ground." So he threw the staff on the ground, and it became a snake; and Moses drew back from it.
4 Then the Lord said to Moses, "Reach out your hand, and seize it by the tail"—so he reached out his hand and grasped it, and it became a staff in his hand—
5 "so that they may believe that the Lord, the God of their ancestors, the God of Abraham, the God of Isaac, and the God of Jacob, has appeared to you."