Deuteronomy 16:20 That which is altogether just shalt thou follow, that thou mayest live, and inherit the land which the Lord thy God giveth thee.
Although in the present context Moses is speaking to judges and officers in the towns, the Bible makes it clear that doing justice is the response to the Gospel that the Lord expects from all of us. Micah 6:8: “He has told you, O man, what is good, and what does the Lord require of you but to do justice, and to love kindness, and to walk humbly with your God?”
Children complain when they don’t get what they want: “It’s not fair!” Then they grow up and realize that life is not always fair, and we learn to live with it. However, the Christian seeks after justice in all relationships, although we fail in attaining that perfection. Nevertheless, we want to do what is just and right and balance it with kindness and humility. “Seek ye first the kingdom of God and his righteousness.”
Every person, as a sinner, does not follow what is just and always do right. Therefore, we are condemned and shut out of heaven with a Holy God. But the Gospel is the power for “In it [the gospel] the righteousness of God is revealed [Romans 1:17].” Thus, “The just shall live by faith.” Paul revealed, and Luther discovered, that faith is the key that opens heaven to unrighteous sinners like me, because of Christ.
By faith we are just, and by that faith in Christ we live. The Spirit of Christ that came into the believer follows what is just, seeks righteousness, and also is kind and humble. Faith in the Gospel has worked an awesome transformation!