Adam Clarke on Exodus 7:12

Aaron's rod swallowed up their rods - As Egypt was remarkably addicted to magic, sorcery, etc., it was necessary that God should permit Pharaoh's wise men to act to the utmost of their skill in order to imitate the work of God, that his superiority might be clearly seen, and his powerful working incontestably ascertained; and this was fully done when Aaron's rod swallowed up their rods. We have already seen that the names of two of the chief of these magicians were Jannes and Jambres; see Clarke on Exo 2:10 (note), and 2Tim 3:8 (note). Many traditions and fables concerning these may be seen in the eastern writers.