Why does God harden hearts?

The hardening of hearts, as seen with Pharaoh in Exodus, serves to highlight God's supreme authority over human actions. While individuals like Pharaoh can harden their hearts against God's truth, God also exercises His power to harden them for His purposes. This dual-action supports the truth that even in rebellion, God remains sovereign. Romans 9:18 states, 'Therefore hath he mercy on whom he will have mercy, and whom he will, he hardeneth,' illustrating God's prerogative to shape hearts according to His divine plan, ultimately aiming to reveal His power and glory.