Romans 9:19 Thou wilt say then unto me, why does he yet find fault? For who hath resisted his will?
God can justifiably find fault, because in every single instance, without exception, God has permitted the human agent to exercise intelligence, and freedom of choice. That is why he did not prevent Isaac from choosing to go contrary to His revealed will.
Instead, He worked through Isaac’s folly to get His will done. And that is why He did not prevent Jacob and Rebekah from doing the unthinkable, because we are free moral agents, and the intelligent mind is always to be left untrammeled, to make deliberate decisions, either for good, or for evil.
The fact is that God never hardened pharaoh’s heart by preventing him from doing the right thing. At the first interaction with pharaoh, God, through Moses told him to let His people go, and if at that time, the king was disposed to obey, there would have been an entirely different after history of that ill-fated monarch.
Exodus 5:1 And afterward Moses and Aaron went in, and told Pharaoh, thus, saith the Lord God of Israel, Let my people go, that they may hold a feast unto me in the wilderness. 2 And Pharaoh said, who is the Lord, that I should obey his voice to let Israel go? I know not the Lord, neither will I let Israel go.
May The Lord add His blessing to the study of His word. God bless!