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 holds up God’s holy standard before us, and in so doing demonstrates how sinful we are. In this way, the law points us to our need for a Savior and prepares the way for us to rest in Christ alone for right standing with God, rather than trusting in our own works of obedience to save us. God does not grade on a curve. We will all either pass or fail, depending on whether or not we have rendered to him the perfect obedience of which he is worthy.
Of course, in Adam, we all fail. There is no way around that. But one man, Jesus Christ, the last Adam, has obeyed the law at every single point. His entire life was lived in obedience to God, without ever one single deviation from God’s holy standard in thought, word, or deed. Because of his perfect obedience, we have the hope of being credited with righteousness that will secure our standing before God forever. Without God’s law (both as standards written on our hearts and revealed in the form of a covenant to Israel), we would have no way of knowing how far off we have strayed from God’s standard, and thus would have no way of knowing our need of Christ. The law rebukes us in our sin, but the end result is greater joy for us if we accept what God says about us and run to the only hope we have: his promise in the gospel of Jesus Christ.
Suggested passage for family or personal reading: Titus 3:4-7. What is the basis on which God saved us, according to verse 5? What does the word “justified” mean in verse 7? How does the law of God point us to the gospel?