Exodus 4:8

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, hath appeared to thee.

6 And the LORD said furthermore to him, Put now thy 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.

7 And he said, Put thy hand into thy bosom again. And he put his hand into his bosom again, and drew it out of his bosom, and behold, it was turned again as his [other] flesh.

8 And 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.

9 And it shall come to pass, if they will not believe also these two signs, neither hearken to 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].

10 And Moses said to the LORD, O my Lord, I [am] not eloquent, neither heretofore, nor since thou hast spoke to thy servant: but I [am] slow of speech, and of a slow tongue.

11 And the LORD said to him, Who hath made man's mouth? or who maketh the dumb, or deaf, or the seeing, or the blind? have not I the LORD.