Exodus 4:6-8

6And Jehovah said furthermore unto 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 white as snow.

7And he said, Put thy hand into thy bosom again. (And he put his hand into his bosom again; and when he took it out of his bosom, 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.