Exodus 4:6-8

The LORD also said to him, “Put your hand into your robe [where it covers your chest].” So he put his hand into his robe, and when he took it out, his hand was leprous, as white as snow. Then God said, “Put your hand into your robe again.” So he put his hand back into his robe, and when he took it out, it was restored [and was] like the rest of his body. “If they will not believe you or pay attention to the evidence of the first sign, they may believe the evidence of the second sign.