17. If it is true, he says, that we are justified by Christ, then it is impossible for us still to be sinners or to be justified by the law. On the contrary, if this is not true, if we must be justified by observing the law, then it is impossible for us to be justified by Christ. One of these two must be false. Either we are not justified by Christ, or we are not justified by the law. But the truth is that we are justified by Christ, and therefore we are not justified by the law. So Paul reasons that if we seek to be justified by Christ and being justified in this way are still found to be sinners and need the law to justify us, then Christ is nothing but a lawgiver and a minister of sin.
But we are in fact justified and made righteous in Christ, for the truth of the Gospel teaches us that we are not justified by the law but by Christ. Now, if those who are justified in Christ are still found to be sinners—that is, if they still belong to the law and are under the law (as the false apostles taught)—then they are not yet justified. The law accuses them and shows them to be sinners still and requires obedience of them, as necessary to their justification. Therefore, those who are justified in Christ but are still sinners before God are not justified, and so it follows that Christ is not a justifier, but a minister of the law.
In these words, Paul vehemently charges the false apostles with perverting everything, for they make the law into grace and grace into the law; they make Moses into Christ and Christ into Moses. They teach that apart from Christ and all his righteousness, the observance of the law is necessary for justification. And thus we see that by their intolerable perversity they make the law Christ, for in this way they attribute to the law what belongs rightly to Christ. If you do what the law requires, they say, you will be saved; but if you do not, you will not be justified, however much you believe in Christ. Now, if it is true that Christ does not justify us but is the minister of sin (as must follow from their teaching), then Christ is the law, for we gain nothing from him but what we have under the law. So Christ, being the minister of sin, sends us to the law and to Moses, our justifier.
But Christ’s special role is to raise up again those who have been pronounced guilty under the law and to loose them from their sins, if they believe the Gospel. To all who believe, “Christ is the end of the law so that there may be righteousness” (Romans 10:4); he is “the Lamb of God, who takes away the sin of the world” (John 1:29). It is monstrous that our adversaries should be so perverse as to muddle the law with grace and to transform Christ into Moses. Therefore, I often say that this doctrine of faith is very clear, and everyone may easily understand this distinction between the law and grace, as far as the words are concerned, though in practice it is very hard.
We do not dispute whether we ought to do good works, whether the law is holy, righteous, and good, or whether it ought to be kept or not. This is another matter. Our question concerns justification and whether the law justifies or not. Our enemies will not answer this question or make any distinction as we do, but only cry out that good works ought to be done, that the law ought to be observed. We know that well enough. But because there are various different matters, we will not mix them up. That good works ought to be done, we will declare, at the right time. But since we are now on the matter of justification, we set aside here all good works, for which our adversaries so earnestly strive; they take the glory from Christ and ascribe it to works. But if justification comes through the law, it does not come through grace; and then what has Christ achieved by his death, his preaching, his victory over the law, sin, and death, and by sending the Holy Spirit? We must conclude, therefore, that either we are justified by Christ or else we are made guilty sinners through him. But if the law justifies, it follows that everyone who believes in the Lord Jesus Christ is a sinner and is guilty of eternal death, and if he does not fly to the law, doing what it requires, he will not be saved.
The Holy Scriptures, especially the New Testament, often mention faith in Christ and say that whoever believes in him is saved, does not perish, is not judged, has eternal life, and so on (see John 3:16 and 5:24). Saying that people who believe in him are condemned because they have faith without works is to pervert everything, making Christ a destroyer and a murderer, and Moses a saviour. I admit that our adversaries do not use these exact words, but this is in fact what they teach. They say that faith in Christ does not make us free from sin, but only faith combined with love. This is to say that Christ leaves us in our sins and in the wrath of God and makes us guilty of eternal death, whereas if you keep the law, faith justifies you because it has works, without which faith is no help. Therefore, works justify, and not faith, they claim. What pernicious and cursed teaching this is!
Martin Luther, Galatians, Crossway Classic Commentaries (Wheaton, IL: Crossway Books, 1998), 92-93.
The most sinful and imperfect Christian is justified and therefore saved by faith alone, apart from works. Good works give some assurance of true conversion but only the cross and believing in the finished work of Christ will give any final assurance of salvation to anyone. Those churches which reject the doctrine of justification by faith alone are obvious. They always accuse those who preach sovereign grace and justification by faith alone of antinomianism or lawlessness. They heap burdens on the people that they themselves are unable to keep. (Matthew 5:17-20, 48).
Up to this point we have dealt with this first of Paul’s arguments, that either Christ must be the minister of sin or else the law does not justify. When he had finished this argument, he described himself as an example, saying that he had died to that old law by a new law. Now he answers two objections that might have been made against him. His first answer is against the objections of proud people and the offense of the weak. When the forgiveness of sins is preached freely, malicious people slander it (see Romans 3:8—“Let us do evil that good may result”). As soon as these people hear that we are not justified by the law, they say, “Then let us reject the law. If grace abounds where sin abounds, let us abound in sin, so that we may become righteous, and grace may abound even more.” These malicious and proud spirits spitefully and consciously slander the Scriptures and the teachings of the Holy Spirit, just as they slandered Paul while the apostles were alive, to their own destruction, as it says in 2 Peter 3:16.Moreover, weak people who are not malicious are offended when they hear that the law and good works are not necessary for justification. These people must be helped and must be taught that good works do not justify, as well as how they ought to be done and how not to be done. They ought to be done not as the cause but as the fruits of righteousness; when we are made righteous, we ought to do them—not the other way around, doing them when we are unrighteous in order to be made righteous. The tree makes the apple, not the apple the tree.Martin Luther, Galatians, Crossway Classic Commentaries (Wheaton, IL: Crossway Books, 1998), 106-07.