But let us leave the philosophers aside. The law itself, which contains the most perfect rule of life, could not, as we said, confer righteousness. Not that there was anything lacking in the law; Moses declared that he set before the people good and evil, life and death. But because of the corruption of our nature, the law was not enough to insure righteousness. Even as Paul taught (Rom. 8:3), the defect was in our flesh, not in the law. When the law speaks, nature drives us in the opposite direction, and our desires break out with the greater force, like untamed wild elephants, against God’s command. Thus the law works wrath rather than righteousness. The law holds all guilty, and by exposing sin takes away from men every excuse. Therefore we must seek another way to righteousness: the way which is in Christ, whom the law itself set forth as its fulfillment.
The righteousness of the law said, Who does these commandments, shall live in them (Lev. 18:5). But none did them. Therefore there had to be another righteousness; one that Paul taught, from Moses himself: The word is near, in your mouth and in your heart; this is the word of faith which we preach (Rom. 10:8). It is this doctrine that justifies us—not the bare doctrine, but because it offers us the fruit of Christ’s death, by which our sins are forgiven and we are reconciled to God. For if by faith we grasp this gift, we are counted as righteous before God.
—Calvin: Commentaries, trans. Joseph Haroutunian and Louise Pettibone Smith (Philadelphia: Westminster Press, 1958), 156.