For follow-up discussion and general commentary on the topic. Comments are sorted chronologically.
This is very confusing. The God I know is all about love and forgiveness.
He is a God of love, looking always to forgive. But He is, above all, a God of righteousness. Much of the answer given is based on that fact.
However, answers like this leave me unsure. We try to explain why God does what he does, and find ourselves lost very quickly. Whilst it is no answer, it is simply that He is God.
He is not man that we understand Him: Nor are we gods so that He needs to explain himself. He simply IS God. The only God. If he chooses to punish one and free another, He can - and will.
According to some Jewish thought, starting with Nachmindes, God hardened Pharoah's heart in order to *preserve* his free will to choose whether or not to let the Israelites go.
The teaching holds that if Pharoah's heart had not been first hardened, he would have been overwhelmed in fear by the plagues visited and been compelled to offer up the Israelites, much as a man offers up his wallet in exchange for his life.
Yet a man who trades his wallet for his life is not making a truly free choice. In this line of Jewish thought, God goes to great extents to preserve Pharoah's natural will by hardening his heart to remove fear as a factor 'forcing' his hand.
Rather, Pharoahs natural (and selfish) decision making was left in-tact.
Rabbi Naftali Silverburg concludes the matter this way:
"If the benevolent and all-merciful Creator manipulated Pharaoh’s psyche and cognitive abilities to guarantee his ability to choose evil, certainly He does anything necessary to ensure our ability to choose good!
It is very popular to blame a plethora of external factors for one’s shortcomings. But the Torah teaches us that even the most awesome and devastating circumstances don’t affect a person’s G‑d-given freedom of choice."
It is interesting to see this passage, often a comfort to Jews in showing God preserving freedom of choice, is often used as a sign or excuse that God 'made' or makes certain people choose evil.
God wants them to know, that when He says something, He fulfills it. The same chapter and verse explains it very clearly when it says, "I will harden the heart of Pharoah." We later read that He (God) fulfilled it, meaning God means everything He says at any given time.