Exodus 4:18 Moses went back to Jethro his father-in-law and said to him, “Please let me go back to my brothers in Egypt to see whether they are still alive.” And Jethro said to Moses, “Go in peace.” And the LORD said to Moses in Midian, “Go back to Egypt, for all the men who were seeking your life are dead.” So Moses took his wife and his sons and had them ride on a donkey, and went back to the land of Egypt. And Moses took the staff of God in his hand. And the LORD said to Moses, “When you go back to Egypt, see that you do before Pharaoh all the miracles that I have put in your power. But I will harden his heart, so that he will not let the people go. Then you shall say to Pharaoh, ‘Thus says the LORD, Israel is my firstborn son, and I say to you, “Let my son go that he may serve me.” If you refuse to let him go, behold, I will kill your firstborn son.’”
When the fire faded from the burning bush and when the voice of God was silent across the desert, then it was upon Moses to obey, and to do what God told him to do. More than one person has had a spectacular burning bush type experience and then gone on to live as if nothing really happened. Moses made sure that it was clear for him to go. Moses didn’t really tell his father-in-law the story behind his desire to return to Egypt. Perhaps he just felt it was too fantastic and would rather let God demonstrate His Word through fulfilling it. “Even the call of God did not erase the need for human courtesy and respect for one’s father-in-law.”
Sometimes, it says that God hardened the heart of Pharaoh (Exodus 4:21). Sometimes it says that Pharaoh hardened his own heart (Exodus 8:15). Sometimes it says simply that Pharaoh’s heart was hardened, without saying who did it (Exodus 7:13). Who really hardened Pharaoh’s heart? We might say that it was both God and Pharaoh; but whenever God hardened Pharaoh’s heart, He never did it against Pharaoh’s will. Pharaoh never said, “Oh, I want to do what is good and right and I want to bless these people of Israel” and God answered, “No, for I will harden your heart against them!” When God hardened, He allowed Pharaoh’s heart to do what Pharaoh wanted to do – God gave Pharaoh over to his sin (Romans 1:18-32). (Guzik)
We come to the hardening of Pharaoh’s heart and this has been something of a mystery to me but Ellicott has some insight that seems to bring some clarity. “I will harden his heart.—The hardening of Pharaoh’s heart has been the subject of much controversy. It is ascribed to God in this place, and again in Exodus 7:3; Exodus 9:12; Exodus 10:1; Exodus 10:20; Exodus 10:27; Exodus 14:4; Exodus 14:8; to Pharaoh in Exodus 8:15; Exodus 8:32; and Exodus 9:34; to the action of the heart itself in Exodus 7:13; Exodus 7:22; Exodus 9:7; Exodus 9:35. It is conceivable that these may be simply three forms of speech, and that the actual operation was one and the same in every case. Or, three different modes of operation may be meant. It is in favour of the latter view, that each term has a period during which it is predominant. In the narrative of what happened, the action of the heart is itself predominant in the first period; that of Pharaoh on his heart in the second; that of God in the third. We may suppose that, at first, Pharaoh’s nature was simply not impressed, and that then his heart is said to have “hardened itself,” or “remained hard;” that after a while, he began to be impressed; but by an effort of his will controlled himself, and determined that he would not yield: thus “hardening his own heart;” finally, that after he had done this twice (Exodus 8:15; Exodus 8:32), God stepped in and “smote him with a spirit of blindness and infatuation,” as a judgment upon him (Exodus 9:12), thus, finally, “hardening” him (comp. Romans 9:18). This divine action was repeated, on three subsequent occasions (Exodus 10:20; Exodus 10:27; Exodus 14:8), Pharaoh’s time of probation being past, and God using him as a mere means of showing forth His glory. There is nothing in this contrary to the general teaching of the Scriptures, or to the Divine Perfection.”
Gill says about the same; “I will harden his heart, that he shall not let the people go; that is, not directly, not for some time, not until all the wonders are wrought, and plagues inflicted to bring him to it: he first hardening his own heart against God, and all remonstrances made unto him, it was but a righteous thing in God to give him up to the hardness of his heart, to deny him his grace, which only could soften it, and to leave him to the corruptions of his nature, and the temptations of Satan; and by leaving him to strong delusions, to believe the lying miracles of his magicians: this the Lord thought fit to acquaint Moses with, lest he should be discouraged by his refusal to dismiss Israel.”
Keil and Delitzsch commentary explains it with a bit more ease; “Thus Pharaoh would not bend his self-will to the will of God, even after he had discerned the finger of God and the omnipotence of Jehovah in the plagues suspended over him and his nation; he would not withdraw his haughty refusal, notwithstanding the fact that he was obliged to acknowledge that it was sin against Jehovah. Looked at from this side, the hardening was a fruit of sin, a consequence of that self-will, high-mindedness, and pride which flow from sin, and a continuous and ever increasing abuse of that freedom of the will which is innate in man, and which involves the possibility of obstinate resistance to the word and chastisement of God even until death. As the freedom of the will has its fixed limits in the unconditional dependence of the creature upon the Creator, so the sinner may resist the will of God as long as he lives. But such resistance plunges him into destruction, and is followed inevitably by death and damnation. God never allows any man to scoff at Him. Whoever will not suffer himself to be led, by the kindness and earnestness of the divine admonitions, to repentance and humble submission to the will of God, must inevitably perish, and by his destruction subserve the glory of God, and the manifestation of the holiness, righteousness, and omnipotence of Jehovah. The penitent permit the proofs of divine goodness and grace to lead them to repentance and salvation; but the impenitent harden themselves more and more against the grace of God, and so become ripe for the judgment of damnation. The very same manifestation of the mercy of God leads in the case of the one to salvation and life, and in that of the other to judgment and death, because he hardens himself against that mercy. In this increasing hardness on the part of the impenitent sinner against the mercy that is manifested towards him, there is accomplished the judgment of reprobation, first in God’s furnishing the wicked with an opportunity of bringing fully to light the evil inclinations, desires, and thoughts that are in their hearts; and then, according to an invariable law of the moral government of the world, in His rendering the return of the impenitent sinner more and more difficult on account of his continued resistance, and eventually rendering it altogether impossible. It is the curse of sin, that it renders the hard heart harder, and less susceptible to the gracious manifestations of divine love, long-suffering, and patience. In this twofold manner God produces hardness, not only permissive but effective; i.e., not only by giving time and space for the manifestation of human opposition, even to the utmost limits of creaturely freedom, but still more by those continued manifestations of His will which drive the hard heart to such utter obduracy that it is no longer capable of returning, and so giving over the hardened sinner to the judgment of damnation. ”
“The sun, by the force of its heat, moistens the wax and dries the clay, softening the one and hardening the other; and as this produces opposite effects by the same power, so, through the long-suffering of God, which reaches to all, some receive good and others evil, some are softened and others hardened.” – (Theodoret)