In Exodus 9 I notice the mystery of God hardening Pharaoh's heart. In Romans 9:17, Paul will quote from Exodus 9:16 to declare that God's freedom in mercy and hardening is part of His commitment to proclaim the honor of His name everywhere. God is free to have mercy or harden, and yet Pharaoh is also completely guilty. And yet there is no unrighteousness in God. This is a mystery.