Exodus 4:6-8

Furthermore the LORD said to him, “Now put your hand in your bosom.” And he put his hand in his bosom, and when he took it out, behold, his hand was leprous, like snow. And He said, “Put your hand in your bosom again.” So he put his hand in his bosom again, and drew it out of his bosom, and behold, it was restored like his other flesh. “Then it will be, if they do not believe you, nor heed the message of the first sign, that they may believe the message of the latter sign.