An Obvious Question: Why Did God Harden Pharaoh's Heart?

(3) But I will harden Pharaoh’s heart, that I may multiply My signs and marvels in the land of Egypt. (4) When Pharaoh does not heed you, I will lay My hand upon Egypt and deliver My ranks, My people the Israelites, from the land of Egypt with extraordinary chastisements. (5) And the Egyptians shall know that I am יהוה, when I stretch out My hand over Egypt and bring out the Israelites from their midst.” (6) This Moses and Aaron did; as יהוה commanded them, so they did. (7) Moses was eighty years old and Aaron eighty-three, when they made their demand on Pharaoh. (8) יהוה said to Moses and Aaron, (9) “When Pharaoh speaks to you and says, ‘Produce your marvel,’ you shall say to Aaron, ‘Take your rod and cast it down before Pharaoh.’ It shall turn into a serpent.”...(13) Yet Pharaoh’s heart stiffened and he did not heed them, as יהוה had said. (14) And יהוה said to Moses, “Pharaoh is stubborn; he refuses to let the people go. (15) Go to Pharaoh in the morning, as he is coming out to the water, and station yourself before him at the edge of the Nile, taking with you the rod that turned into a snake. (16) And say to him, ‘יהוה, the God of the Hebrews, sent me to you to say, “Let My people go that they may worship Me in the wilderness.” But you have paid no heed until now. (17) Thus says יהוה, “By this you shall know that I am יהוה.” See, I shall strike the water in the Nile with the rod that is in my hand, and it will be turned into blood; (18) and the fish in the Nile will die. The Nile will stink so that the Egyptians will find it impossible to drink the water of the Nile.’”... (22) But when the Egyptian magician-priests did the same with their spells, Pharaoh’s heart stiffened and he did not heed them—as יהוה had spoken. (23) Pharaoh turned and went into his palace, paying no regard even to this.

AND THE MAGICIANS OF EGYPT DID IN LIKE MANNER WITH THEIR SECRET ARTS. Now, there is a great difference between what Aaron did and what the magicians brought about. Aaron transformed all of the Nile that was before him plus all the water that was in all the borders of Egypt, which he did not see. Furthermore, he changed water that was not standing still but was continually running, with other water taking its place, into blood. Additionally, the plague lasted for seven days. The magicians, on the other hand, were only able to transform a little water standing in a vessel, for a moment, until Pharaoh returned to his house.

ויחזק לב פרעה, “Pharaoh’s heart remained obstinate;” seeing that his sorcerers had been able to duplicate Aaron’s feat, he concluded that Aaron was another sorcerer.

ואני אקשה AND I WILL ALLOW [PHARAOH’S HEART] TO HARDEN — Since he has wickedly resisted Me, and it is manifest to Me that the heathen nations find no spiritual satisfaction in setting their whole heart to return to Me penitently, it is better that his heart should be hardened in order that My signs may be multiplied against him so that he may recognize My divine power.

ואני אקשה, seeing that God is interested in the sinner’s repentance rather than his death, God told Moses that He would bring on numerous plagues, all in order to increase the chances that Pharaoh would finally see the light and become a genuine penitent. He hoped that by demonstrating greatness and power this would eventually cause the Egyptians to recognise all this.

AND I WILL HARDEN PHARAOH’S HEART. The question arises: “If God hardened Pharaoh’s heart what was his transgression and what was his sin?” The answer is: God granted wisdom to man and implanted in his heart the intelligence to receive power from on high to add to his good or to diminish his evil.