23. Paul goes on to explain how the law profits us, and its necessity. He has already said that it was added because of transgressions-not that it was God’s principle purpose to make a law that would bring death and damnation (see Romans 7:13). The law is a word that shows life and drives people to it. Therefore, it is not only given as a minister of death, but its chief purpose is to reveal death, so that people might see and know how horrible sin is. Still, it is not as though the law served no purpose but to kill and destroy; it reveals death in order that when people are terrified and cast down and humbled, they should fear God (Exodus 20:20). The function of the law is to kill, and yet in such a way that God may revive and bring to life again. Because people are proud and dream they are wise, righteous, and holy, it is necessary for them to be humbled by the law, so that the beast that is their high opinion of their righteousness might be slain; otherwise no one can obtain life.
So although the law kills, God uses this effect of the law, this death, for a good purpose—to bring life. God sees that this universal plague of the whole world—namely, our high opinion of our own righteousness, our hypocrisy, and our confidence in our own holiness—could not be beaten down by any other means. He wants our self-reliance to be killed by the law—not forever, but so that once it is killed, we might be raised up again, above and beyond the law, and then might hear this voice: “Fear not. I have given the law and killed you by the law not so that you would remain in this death, but so that you would fear me and live.” To rely on good works and righteousness is inconsistent with the fear of God; and where there is no fear of God, there can be no thirsting for grace or life. God must therefore have a strong hammer to break the rocks and a hot burning fire in the midst of heaven to overthrow the mountains-that is, to destroy this furious and obstinate beast, this presumption. When we are brought to nothing by this bruising and breaking, we may despair of our own strength, righteousness, and holiness; then we will thirst after mercy and forgiveness of sins. Galatians, Martin Luther, The Crossway Classic Commentaries Series, Series Editors McGrath, Alister; Packer, J.I., p. 180