The king’s free will
Jewish thinkers believe that human beings forge their own destiny. Their b’chirah chofshit (free will) enables them to choose what sort of human beings to be and what to make of their lives.
Why then did God withhold that choice from Pharaoh and harden his heart (Exodus 7:3)?
The answer is that Pharaoh was not a baby whose disposition and character were not yet known. He was an adult and there were already plenty of signs that he was rigid in his thinking, arrogant, self-confident and far from modest or humble. Pharaoh basically said, “I am the greatest! Don’t talk to me about your God!”
It was not that God made the king’s heart hard – it was hard already. It is not that God made him callous – he was callous already.
What God did was to reinforce the hard-heartedness and callousness and teach him a lesson by saying, as it were, “You want to be stubborn? I’ll make you even more stubborn! I’ll show you what ‘stubborn’ really means!”
Anyone else might be pricked by feelings of conscience – but not Pharaoh… Anyone else might have felt uneasy about enslaving the Israelites – but not Pharaoh…
In the end Pharaoh brought ruin on his land and destroyed himself and his people.