Exodus 7:3-4 says, “But I will harden Pharaoh's heart, and though I multiply my miraculous signs and wonders in Egypt he will not listen to you. Then I will lay my hand on Egypt and with mighty acts of judgment I will bring out my people the Israelites.” It seems unjust for God to harden Pharaoh’s heart and then to punish Pharaoh and Egypt for what Pharaoh decided when his heart was hardened. Why would God harden Pharaoh’s heart just so He could judge Egypt more severely with additional plagues?
First, Pharaoh was not an innocent or godly man. He was a brutal dictator overseeing the terrible abuse and oppression of the Israelites, who likely numbered over 1.5 million people at that time. The Egyptian pharaohs had enslaved the Israelites for 400 years. A previous pharaoh—possibly even the pharaoh in question—ordered that male Israelite babies be killed at birth (Exodus 1:16). The pharaoh God hardened was an evil man, and the nation he ruled agreed with, or at least did not oppose, his evil actions.
Second, before the first few plagues, Pharaoh hardened his own heart against letting the Israelites go. “Pharaoh's heart became hard” (Exodus 7:13, 22; 8:19). “But when Pharaoh saw that there was relief, he hardened his heart” (Exodus 8:15). “But this time also Pharaoh hardened his heart” (Exodus 8:32). Pharaoh could have spared Egypt of all the plagues if he had not hardened his own heart. God was giving Pharaoh increasingly severe warnings of the judgment that was to come. Pharaoh chose to bring judgment on himself and on his nation by hardening his own heart against God’s commands.
As a result of Pharaoh’s hard-heartedness, God hardened Pharaoh’s heart even further, allowing for the last few plagues (Exodus 9:12; 10:20, 27). Pharaoh and Egypt had brought these judgments on themselves with 400 years of slavery and mass murder. Since the wages of sin is death (Romans 6:23), and Pharaoh and Egypt had horribly sinned against God, it would have been just if God had completely annihilated Egypt. Therefore, God’s hardening Pharaoh’s heart was not unjust, and His bringing additional plagues against Egypt was not unjust. The plagues, as terrible as they were, actually demonstrate God’s mercy in not completely destroying Egypt, which would have been a perfectly just penalty.
Romans 9:17-18 declares, “For the Scripture says to Pharaoh: ‘I raised you up for this very purpose, that I might display my power in you and that my name might be proclaimed in all the earth.’ Therefore God has mercy on whom He wants to have mercy, and He hardens whom He wants to harden.” From a human perspective, it seems wrong for God to harden a person and then punish the person He has hardened. Biblically speaking, however, we have all sinned against God (Romans 3:23), and the just penalty for that sin is death (Romans 6:23). Therefore, God’s hardening and punishing a person is not unjust; it is actually merciful in comparison to what the person deserves.