Exodus 4:6-8

Then the LORD said, “Put your hand inside your cloak.” So Moses put his hand into his cloak, and when he took it out, the skin was leprous—it had become as white as snow. “Now put it back into your cloak,” he said. So Moses put his hand back into his cloak, and when he took it out, it was restored, like the rest of his flesh. Then the LORD said, “If they do not believe you or pay attention to the first sign, they may believe the second.