Exodus 4:2-5

2And Jehovah said unto him, What is that in thy 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 Jehovah said unto Moses, Put forth thy hand, and take it by the tail: (and he put forth his hand, and laid hold of it, and it became a rod in his hand);

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