Exodus 4

1 Then Moses answered and said, “But suppose they will not believe me or listen to my voice; suppose they say, ‘The Lord has not appeared to you.’” 2 So the Lord said to him, “What is that in your hand?” He said, “A rod.” 3 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. 4 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), 5 “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.” . . .
— EXODUS 4