So Moses and Aaron went to Pharaoh and did just as the LORD commanded. Aaron cast down his staff before Pharaoh and his servants, and it became a serpent.
10. And Moses and Aaron went in. Although they were now fully conscious of their vocation; and knew that they were endued with divine power for working miracles, yet would they never have dared to approach the fierce and cruel tyrant, unless the inward inspiration of the Spirit had armed them to persevere.
Pharaoh demands a miracle not to be convinced but hoping none will come, so he can cloak his unbelief. The rod becomes a serpent to strike terror into him, for God deals with sinners gradually, making them fear before they feel. Yet the magicians' imitation dulls the force of what should have broken his heart.
AI summary
Commenting on Exodus 7:8-13
And Moses and Aaron went in unto Pharaoh,.... Into the palace of Pharaoh boldly, and with intrepidity, clothed with such power and authority, and assured of success: and they did as the Lord had commanded; they demanded in his name the dismission of the children of Israel, and upon his requiring a miracle to confirm their mission, wrought one as follows: and Aaron cast down...