How do we know that God is a righteous judge?

God is described as righteous in that He does not compromise His holy character. His righteousness is on full display at the cross, where Christ, without sin, took upon Himself the punishment of sin for those He came to save. In this way, God's just nature is perfectly aligned with His mercy. Romans 8:33 affirmatively states that it is God that justifies, meaning that God does not act capriciously, but rather maintains His justice while granting mercy. This balancing act of justice served and mercy granted showcases the absolute righteousness of God as He addresses the problem of sin within His elect.