Galatians 2:16
Knowing that a man is not justified by the works of the law, but by the faith of Jesus Christ, even we have believed in Jesus Christ, that we might be justified by the faith of Christ, and not by the works of the law: for by the works of the law shall no flesh be justified.
No one is justified, made righteous, or saved by works of the law, but only by faith in Jesus Christ, for by the works of the law no flesh will be justified. No keeping of the law can justify, because the law cannot save one who has transgressed it. Salvation does not come through the law and religious rites apart from faith, and ceremonial observance cannot be made essential to salvation.
The law reveals sin, and its perfect standard cannot be lowered to human weakness. For one who has transgressed it the law cannot give pardon or salvation but brings condemnation. No one can make himself righteous by his own efforts or be made righteous by doing the works of the law.
Christ paid the sinner's debt, bore the penalty of transgression and satisfied justice, so sinners may receive His righteousness by faith and claim the merits of His blood. He is the sinner's Advocate with the Father. He is the reality foreshadowed by the Jewish services, which cannot save apart from living faith in Him.
The faith required is living faith that includes repentance. It means receiving Christ and remaining in Him rather than relying on one's own works.
The justification promised does not excuse continued sin and does not weaken or change the law but upholds it. The moral law contains the gospel in principle. Treating faith in Christ and obedience to the Ten Commandments as minor matters distorts the gospel.
Righteousness by faith in Christ belongs together with kindred truths, and churches are dying for want of teaching on this subject. Perfection will not be found in any man's investigations of it.
The truth of justification by faith was held by Paul and Augustine, by Huss the Bohemian Reformer a century before Luther, and by Luther. Judgment will come upon the world for having this preached truth burned.
Grasping that people are justified and saved through faith in Christ and not by works leads to the further conclusion that papal authority is not from God. That consequence may not be recognized at once.