Why does God show mercy to some and harden others?

The question of why God shows mercy to some while hardening others is critical for understanding His sovereign plan. Romans 9:22-23 reveals that God endures with much patience vessels of wrath prepared for destruction, in order to make known the riches of His glory on vessels of mercy prepared beforehand for glory. This divine action underscores the grandeur of God’s sovereignty, which aims to manifest His glory through both mercy and judgment. This is essential for Christians as it reassures them of God's ultimate purposes, even amidst suffering and mystery in this present life.