Exodus 4:6-8

The LORD furthermore said to him, “Now put your hand into your bosom.” So he put his hand into his bosom, and when he took it out, behold, his hand was leprous like snow. Then He said, “Put your hand into your bosom again.” So he put his hand into his bosom again, and when he took it out of his bosom, behold, it was restored like the rest of his flesh. “If they will not believe you or heed the witness of the first sign, they may believe the witness of the last sign.