Pharoah had already shown his contempt for Moses, Aaron, the Hebrews (all slaves) and their God. Pharoah’s heart was already hard, and the natural consequence was about to be played out:
Romans 1:28-31 And even as they did not like to retain God in their knowledge, God gave them over to a debased mind, to do those things which are not fitting; being filled with all unrighteousness, sexual immorality, wickedness, covetousness, maliciousness; full of envy, murder, strife, deceit, evil-mindedness; they are whisperers, backbiters, haters of God, violent, proud, boasters, inventors of evil things, disobedient to parents, undiscerning, untrustworthy, unloving, unforgiving, unmerciful;
So when God told Moses what this process would look like—that God had hardened Pharoah’s heart—Moses would have had to have known there would be no point in asking Why can’t Pharoah just change? We’re not asking for much … .
A changed and merciful Pharaoh wasn’t going to happen:
Exodus 7:3-5 But I will make Pharaoh’s heart stubborn so I can multiply my miraculous signs and wonders in the land of Egypt. Even then Pharaoh will refuse to listen to you. So I will bring down my fist on Egypt. Then I will rescue my forces—my people, the Israelites—from the land of Egypt with great acts of judgment. When I raise my powerful hand and bring out the Israelites, the Egyptians will know that I am the Lord.
Could Pharaoh have changed if he wanted to? Well, yes. Pharaoh could have humbly accepted what Moses was saying about God’s plans and let go of Egypt’s slave labour force.
But it would have meant accepting defeat at the hands of a returned murderer and leader of slaves, and a despised Hebrew who could do nothing Pharaoh’s own magicians couldn’t at least partly copy. It was a tough call at this stage:
7:13 Pharaoh’s heart, however, remained hard. He still refused to listen, just as the Lord had predicted.