The first five plagues the magicians had tried to imitate, and partly they had succeeded. But in this sixth plague they could not stand before Moses, and thenceforth they gave up the attempt to do as he did. Their craft had all along been harmful to themselves. Although they could produce the plagues, they could not imitate Moses in causing them to disappear. They would put their hands into their bosom, and draw them out white with leprosy, exactly like Moses, but their flesh remained leprous until the day of their death. And the same happened with all the other plagues that they imitated: until their dying day they were afflicted with the ills they produced.
Egyptian Magicians Could Not Match the Sixth Plague
Legends of the Jews 4:307