The law should drive us to Jesus Christ as our only hope of salvation. “The law is a kind of mirror,” wrote John Calvin (Inst. 2.7.7). In the light of its perfection we see our sin and failure. The church father Augustine wrote: “If the Spirit of grace is absent, the law is present only to convict and slay us.” (On Rebuke and Grace, I.2) The law accuses sinners; and so it should convince us that we are spiritually sick and helpless, so that we start looking eagerly for the medicine of God’s grace, which is Jesus Christ. (Augustine, To Asselius, 200)
This is an all-important use of the law. But Luther, Calvin, and other Reformers recognized that this is not the only way in which we use God’s law. They recognized three “uses of the law”.
The first use of the law is as a mirror, so that we recognize our sin. But the second use of the law is to curb evil in the world. Even wicked people, who have no faith in Jesus, may take God’s law seriously as a deterrent, if only out of fear of punishment. Sometimes the Lord uses this curbing of wickedness as a first step on the way to repentance and true faith. (Calvin, Inst. 2.7.11)
The third use of the law is to show us how to live a God-honouring life. Believers, who have received the Holy Spirit, are eager to do what is right; and the law shows how to please God. The Heidelberg Catechism deliberately placed the law toward the end, in the section of “our gratitude”. For believers, the law is no longer a curse, but it becomes a guide for the new life that Jesus Christ has given them. Calvin suggests that the law sometimes even “acts like a whip to the flesh, urging it on, as men do lazy sluggish donkey.” (Inst. 2.7.12)
Of these three uses of the law, the first and third are the most important. We should leave them in the proper order. First the law must bring us to our knees, to confess that we cannot keep it perfectly, and to ask for the grace of Jesus Christ. Not our righteousness, but his righteousness. Only then, when the Spirit works faith in the heart of the believer, can the law play a positive role. We love the law, because it shows us how we can please God. Not to earn our salvation; but to live out that salvation in a way that brings glory to God and is good for us.