Question: "What does it mean that God is a God of justice?"
Answer: Justice is a term used for what is right or “as it should be.” Justice is one of God’s attributes and flows out of His holiness. Justice and righteousness are often used synonymously in the Bible. Since righteousness is the quality or character of being right or just, it is another attribute of God and incorporates both His justice and holiness.
We cannot begin to understand God’s justice unless we first understand sin. Sin is lawlessness (1 John 3:4) and iniquity (Daniel 9:4-5; Micah 2:1; James 3:6). It embodies everything contrary to God’s holy nature and is offensive to Him. Thus, sin is a crime against God, and justice demands a penalty of death and separation from Him for it (Romans 1:18-32; 2:5; 3:23). But God sent His Son, Jesus Christ, to earth to pay that penalty for us (Romans 5:8-11; 6:23) and made salvation available to all who believe in His name (John 1:12; 3:15-17; 20:31).
God’s own righteousness is provided as a gift to sinners who accept Jesus Christ as their Savior and is based upon His grace and mercy in response to our faith (Romans 3:23-26; Ephesians 2:3-7). His mercy and grace are not in spite of His justice, but because of it. He loved us so much that, despite the fact that our sin demands our death, He sent His Son to be our substitute upon the cross, thus demonstrating that His justice was not violated, but instead satisfied (1 Thessalonians 1:10; 5:9).
Having been made in His image (Genesis 1:26-27), we humans long for moral justice to prevail upon the earth and are outraged when we see injustice happening around us. Why do we seek justice for crimes? It’s in our DNA. King David’s outrage when the poor man’s lamb was taken away by the rich man resonates within us (2 Samuel 12:1-14). That is why Nathan told the story to David in the first place because it revealed David’s own injustice in taking Uriah’s wife from him. David’s immediate repentant prayer was effective because by admitting his sin against God, he acknowledged the righteousness of God. The Lord told David through the prophet Nathan that even though his sin was forgiven, the child resulting from the adulterous affair would die, demonstrating the fact that his sin still had to be judged.
As for the future, the book of Revelation reveals the justice of God in all its glory during the end times. When the saints watch the destruction of the earth, their song will be of God’s righteous judgment upon the inhabitants for their ultimate sin of rejecting Him (Revelation 11:16-18; 15:3-4; 16:7; 19:1-4). And as 2 Peter 3:13 says, we are promised that someday, when Christ physically reigns on earth, God’s righteous justice will finally be on full display.