Charles Ellicott Commentary Exodus 10:1

"And Jehovah said unto Moses, Go in unto Pharaoh: for I have hardened his heart, and the heart of his servants, that I may show these my signs in the midst of them," — Exodus 10:1 (ASV)

I have hardened ... the heart of his servants. —They, too, had first hardened their own hearts (Exodus 9:34), and so deserved a penal hardening. A certain amount of responsibility rested on them. Had they allowed the miracles to have their full natural effect upon their minds, they would have been convinced that resistance was useless, and would have impressed their views upon the Pharaoh. Even in the most absolute governments public opinion has weight, and the general sentiment of the Court almost always carries the sovereign with it.

That I might shew these my signs. —There is nothing derogatory to the Divine Nature in a penal hardening being, as it were, utilised to increase the glory of God, and affect for good future generations of His people. The accumulation of plague upon plague, which the obduracy of Pharaoh and his subjects brought about, was of vast importance in presenting to Israel, and even to the surrounding nations, a manifestation of the tremendous power of God, calculated to impress them as nothing else would have done.