How do we know that God is a just and merciful God?

The relationship between God's justice and mercy is most clearly illustrated through the crucifixion of Jesus Christ. Justice requires that sin be judged, which God fulfills by punishing sin in His Son on the cross—a substitutionary sacrifice for His people. This act upholds God's holiness and justice while simultaneously revealing His mercy; therefore, He can justly forgive sinners. Romans 3:26 encapsulates this by stating that God is both 'just and the justifier of the one who has faith in Jesus.' This confluence of justice and mercy is fundamental to understanding God's nature in the context of salvation.