Exodus 4:2-9

2And Yhwh 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 Yhwh 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 Yhwh God of their fathers, the God of Abraham, the God of Isaac, and the God of Jacob, hath appeared unto thee.

6And Yhwh said furthermore unto him, Put now thine hand into thy bosom. And he put his hand into his bosom: and when he took it out, behold, his hand was leprous as snow. 7And he said, Put thine hand into thy bosom again. And he put his hand into his bosom again; and plucked it out of his bosom, and, behold, it was turned again as his other flesh. 8And it shall come to pass, if they will not believe thee, neither hearken to the voice of the first sign, that they will believe the voice of the latter sign. 9And it shall come to pass, if they will not believe also these two signs, neither hearken unto thy voice, that thou shalt take of the water of the river, and pour it upon the dry land: and the water which thou takest out of the river shall become blood upon the dry land.1