Exodus 4:2-5

2And the Lord said unto him, What is that in thine hand? And he said, A rod.

3And he said, Cast it on the ground. And he cast it on the ground, and it became a serpent; and Moses fled from before it.

4And the Lord said unto Moses, Put forth thine hand, and take it by the tail. And he put forth his hand, and caught it, and it became a rod in his hand:

5That they may believe that the Lord God of their fathers, the God of Abraham, the God of Isaac, and the God of Jacob, hath appeared unto thee.