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.

But the LORD hardened Pharaoh's heart, and he would not let them go.

10:21-29 The plague of darkness brought upon Egypt was a dreadful plague. It was darkness which might be felt, so thick were the fogs. It astonished and terrified. It continued three days; six nights in one; so long the most lightsome palaces were dungeons. Now Pharaoh had time to consider, if he would have improved it. Spiritual darkness is spiritual bondage; while Satan blinds men's eyes that they see not, he binds their hands and feet, that they work not for God, nor move toward heaven. They sit in darkness. It was righteous with God thus to punish. The blindness of their minds brought upon them this darkness of the air; never was mind so blinded as Pharaoh's, never was air so darkened as Egypt. Let us dread the consequences of sin; if three days of darkness were so dreadful, what will everlasting darkness be? The children of Israel, at the same time, had light in their dwellings. We must not think we share in common mercies as a matter of course, and therefore that we owe no thanks to God for them. It shows the particular favour he bears to his people. Wherever there is an Israelite indeed, though in this dark world, there is light, there is a child of light. When God made this difference between the Israelites and the Egyptians, who would not have preferred the poor cottage of an Israelite to the fine palace of an Egyptian? There is a real difference between the house of the wicked, which is under a curse, and the habitation of the just, which is blessed. Pharaoh renewed the treaty with Moses and Aaron, and consented they should take their little ones, but would have their cattle left. It is common for sinners to bargain with God Almighty; thus they try to mock him, but they deceive themselves. The terms of reconciliation with God are so fixed, that though men dispute them ever so long, they cannot possibly alter them, or bring them lower. We must come to the demand of God's will; we cannot expect he should condescend to the terms our lusts would make. With ourselves and our children, we must devote all our worldly possessions to the service of God; we know not what use he will make of any part of what we have. Pharaoh broke off the conference abruptly, and resolved to treat no more. Had he forgotten how often he had sent for Moses to ease him of his plagues? and must he now be bid to come no more? Vain malice! to threaten him with death, who was armed with such power! What will not hardness of heart, and contempt of God's word and commandments, bring men to! After this, Moses came no more till he was sent for. When men drive God's word from them, he justly gives them up to their own delusions.