Exodus 4:6-9

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. But if they will not believe these two signs or pay attention to what you say, you are to take some water from the Nile and pour it on the dry ground; and the water which you take out of the river will turn into blood on the dry ground.”