But the Lord hardened Pharaoh's heart. A probable conjecture may be elicited from hence, that at the coming of Moses some light shone forth, so that the darkness was not so thick; because Pharaoh would never have dared to boast himself so proudly without being confident of impunity; but his pretences at the commencement (of their interview) are here omitted by Moses, though the mitigation of the horrible punishment which had urged him to supplication depended upon them. But although he is still in a state of alarm, still he is hardened, and prepares himself for every extremity rather than simply to obey God. Here, also, according to his custom, Moses asserts that God was the author of his obduracy; not because he inspired with obstinacy a heart otherwise disposed to docility and obedience, but because He gave over as a slave to Satan a reprobate who was willfully devoted to his own destruction, that he might rush forward with still increasing pertinacity in his impiety. But, since Moses has so often used this word, I am astonished at the boldness of certain sophists who, by the substitution of the word permission, allow themselves by this frivolous evasion to escape so plain a statement.

The Lord hardened Pharaoh's heart - He had yet another miracle to work for the complete conviction of the Egyptians and triumph of his people; and till that was wrought he permitted the natural obstinacy of Pharaoh's haughty heart to have its full sway, after each resistance of the gracious influence which was intended to soften and bring him to repentance.

But the Lord hardened Pharaoh's heart,.... Yet more and more:
and he would not let them go; his heart was set against it, his will was resolute, and he was determined never to let them go.

At this demand, Pharaoh, with the hardness suspended over him by God, fell into such wrath, that he sent Moses away, and threatened him with death, if he ever appeared in his presence again. "See my face," as in Genesis 43:3. Moses answered, "Thou hast spoken rightly." For as God had already told him that the last blow would be followed by the immediate release of the people, there was no further necessity for him to appear before Pharaoh.