Exodus 4: 21 And the Lord said unto Moses, When you go to return into Egypt see that you do all those wonders before Pharaoh, which I have put in thine hand: but I will harden his heart, that he shall not let the people go.
In the study of “How and why pharaoh’s heart was hardened”, we should keep in mind that God is A God of love, who was more than willing to let His prediction fail if the ill-fated king would do as the Ninevites did. In the narrative, we would read in several passages where God hardened Pharaoh’s heart, and then we would read where pharaoh hardened his own heart, and therefore, we may safely conclude that the king was hardened in two ways, by himself, and by God, according to the scriptures.
Question: Was Pharaoh always a knuckle-head, long before there were plagues upon Egypt or did God deliberately make him a knuckle-head? Answer: Long before any plague had fallen in Egypt, pharaoh had decided to reject the truth, the facts and evidence that God had given to the nation.
The history of what Joseph had done, in saving the Egyptians by the power of God, surely must have been registered in the national archives, as well as in the minds of the people, but this particular king chose not to see, or recognize the great things God did for the nation.
Exodus 7:22 And the magicians of Egypt did so with their enchantments: and Pharaoh's heart was hardened, neither did he hearken unto them; as the Lord had said.
May The Lord add His blessing to the study of His word. God bless!