Exodus 7:11

Moses had been originally instructed in the learning of the Egyptians, and was suspected to have improved in magical arts in his long retirement. The magicians are therefore sent for to vie with him. The two chief of them were Jannes and Jambres. Their rods became serpents, probably by the power of evil angels, artfully substituting serpents in the room of the rods, God permitting the delusion to be wrought for wise and holy ends. But the serpent which Aaron's rod was turned into, swallowed up the others: which was sufficient to have convinced Pharaoh on which side the right lay.