How do we know that God is a God of justice?

Scripture consistently reveals God as a holy God who will not overlook sin. In Joshua 8, the consequences faced by Ai demonstrate God's justice in punishing disobedience. The Bible teaches that the soul who sins shall die, affirming that God demands justice. Proverbs 17:15 makes it clear that both justifying the wicked and condemning the just are abominations to God. Therefore, understanding God's justice is crucial for grasping the necessity of Christ's sacrifice; only through Christ can believers escape the punishment due for their sins and be declared righteous before God.