How do we know that God is just in His mercy?

God's justice in His mercy stems from His sovereign nature. According to Romans 9:14, the question of whether there is injustice with God is quashed by the assertion that God cannot be unjust. His ways and decisions, including whom He chooses to save, are beyond human comprehension but are grounded in His righteousness. As discussed, God does not owe mercy to anyone; rather, He chooses to extend it. This affirms that the measure of His justice is not comparable to human standards because God's decisions are always aligned with His unchanging character, which is holy and just.