We’ve been going through the New City Catechism as a church as we explore the fundamental Biblical teachings.  This past Sunday we looked at question #15

Question 15 Since no one can keep God’s 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.

Romans 3:20 For by works of the law no human being will be justified in his sight, since through the law comes knowledge of sin.

Commentary by Ligon Duncan

The law of God helps us to know God, know ourselves, know our need, and know the life of peace and blessedness. It helps us to know God because it specifically reveals his character and his attributes, his holy will, what he’s like.

God’s law also reveals to us ourselves, especially our sinful nature and our disobedience, our inclination to sin. For instance, when Jesus is talking to the rich young ruler, he says, “Go, sell what you possess, and give to the poor” (Matt. 19:21). And the rich young ruler essentially says to Jesus, “I can’t.” And he walks away sadly. Now what’s going on in that story? Is Jesus saying that we all have to give away all of our possessions? No. But in the case of the rich young ruler, Jesus is revealing to him by the law of God the specific nature of his own sin. What’s the first commandment? To have no other gods before me. And there, God in the flesh is saying to the rich young ruler, “What’s it going to be? Your money, your possessions, or me, God?” And the rich young ruler chooses something over God, before God.

That leads to the third thing that the law helps us with. It helps us to understand our need. When we know who God is, and we know that we don’t measure up to his morality and character, when we know who we are, and we know the sinful inclinations of our hearts, it presses us to Jesus, because we know that we have need of a Savior. And the Savior has fulfilled that law. He’s obeyed it perfectly, and he’s paid the penalty that is due to us for it. The law presses us to the Savior. It points us to the Savior. It takes us to the Savior.

Of course, the law also shows us the life of peace and blessedness. When we think about obedience, many of us immediately think, “Oh, do I have to? Do I have to do good works? Do I have to obey?” That wasn’t Jesus’s attitude toward God’s commands and God’s will. In fact, he frequently said to his disciples, “My food is to do the will of him who sent me” (John 4:34). In other words, he was saying that it was like spreading a seven-course banquet in front of him to be able to obey the law of God, the will of God. And once we’re redeemed, once we’ve trusted in Jesus Christ alone for salvation as he has offered in the gospel, the law not only is something that points us to Christ, but it also shows us how to live the life of peace and blessedness.