And he hardened Pharaoh’s heart, that he hearkened not unto them; as the LORD had said.
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 he hardened Pharaoh's heart,.... Or, "notwithstanding the heart of Pharaoh was hardened" (a); though he saw the rods of his magicians devoured by rod; or "therefore" (b) his heart was hardened, because he saw that the rods of his magicians became serpents as well as Aaron's; in which there was a deception of sight, and which was suffered for the hardening of his heart...
And he hardened Pharaoh's heart - ויחזק לב פרעה vaiyechezak leb Paroh, "And the heart of Pharaoh was hardened," the identical words which in Exo 7:22 are thus translated, and which should have been rendered in the same way here, lest the hardening, which was evidently the effect of his own obstinate shutting of his eyes against the truth, should be attributed to God. See Clarke's note on Exo 4:21.