Twice now, God says to Moses, "I will harden Pharaoh's heart." (Exodus 4:21; 7:3). What choice does Pharaoh have then? Fifteen hundred years later, the apostle Paul answers the question. Sort of. In Romans 9:20-21, Paul writes, "But who are you, O man, to answer back to God? Will what is molded say to its molder, 'Why have you made me like this?' Has the potter no right over the clay, to make out of the same lump one vessel for honorable use and another for dishonorable use?" In other words, God is God and you're not. Not a terribly satisfying answer, but then, God does not have to satisfy me.
Still there is more. Going back to the plagues, God hardened Pharaoh's heart times, but in six plagues, Pharaoh hardened his own heart. God is in charge, but Pharaoh cooperates. He is not a witless pawn.
Now the 'why' question: Why would God want Pharaoh to stubbornly resist? The answer is in the first commandment, "You shall have no other gods before me." At the time, everybody had gods. Lots of them. So, the One and Only God of Abraham, Isaac, and Jacob, wanted to demonstrate that he is God like no other. The first couple plagues, the Egyptian magicians were able to mimic the work of God, but they couldn't keep up. By the third plague, they admitted, "This is the finger of God," and God continued seven more plagues to hammer that home. The Egyptians would never forget the Hebrew God, and the Israelites would always remember the God who delivered them from bondage.
My God, the Beginning and the End, the First and the Last, the One and Only Creator of the heavens and the earth, You alone I worship and adore. Your ways are good and there is none like You. Why would I ever seek good from another source?
May Your Name be known always in my house. May You always be God of my family--we seek no other. May my children and my children's children (someday!) follow You and worship You. You are my Lord and Savior. I will always remember.