New City Catechism 15.3
Question 15: Since no one can keep the law, what is its purpose?
Answer: That we may know the holy nature and will of God, and the sinful nature and disobedience of our hearts; and thus our need of a Savior. The law also teaches and exhorts us to live a life worthy of our Savior.
The law of God points out our sins and points us to Christ. In this way, the law serves the gospel. But what if we are already believers in Christ? What is the law’s role for us then? First, it is important to remember that, as long as we are in this age, even as believers we never move past the need to have our sins exposed to drive us, again and again, to Christ as our only hope. We do not leave all sin behind at the moment of conversion. We begin a lifelong battle against it, and thus we begin a lifelong battle of fighting to trust in Jesus Christ for the forgiveness of all our sins. John encouraged his readers to confess their sins to God freely with the assurance that God is faithful and just to forgive us when we do (1 John 1:9). Furthermore, while he wrote his first letter in part to help believers fight against sin, he reminds us at the same time that if anyone does sin, we have an advocate who is interceding for our forgiveness (1 John 2:1-2).
Second, believers must be people who truly delight in God’s law. As David wrote in Psalm 119:14-16: “In the way of your testimonies I delight as much as in all riches. I will meditate on your precepts and fix my eyes on your ways. I will delight in your statutes; I will not forget your word.” David wrote these words about the law God had given to Moses in the form of the Mosaic Covenant. As new covenant believers, we are no longer under that covenant. However, that does not mean its precepts are meaningless to us. The law of Moses is not our master, but it is a teacher of wisdom to us. It teaches about who our God is and what he values. In so doing, it points us not only to Jesus as our Redeemer, but as our supreme moral teacher as well, for Jesus did not come to abolish the law but to fulfill it by his life and teaching (Matt. 5:17). As believers in Christ, we are not under the law. Nevertheless, we should love the law of God, for it is holy, righteous, and good (Rom. 7:12).
Suggested passage for family or personal reading: Psalm 19. What does David say about how God has revealed himself in creation? What does he say about God’s revelation of himself through his written word? What does this psalm teach us about the value of God’s law and how we should respond to it?