1. In relation to society, the law issues a standard for right and wrong (the civil use of the law).
God’s law promotes righteousness in the society and protects the people from wrongdoers (Rom. 13:1-7; 1 Tim. 2:1-2). For instance, the law commands us not to bear false witness against our neighbor in order to promote honesty and in order to protect us from dishonest people (Exod. 20:16). The moral law then provides a standard for good and evil in our land. It commends good and condemns evil.
2. In relation to salvation, the law informs sinners of their sin and need of a Savior (the evangelical use of the law).
- The law proclaims our guilt for we have transgressed God’s law. “Through the law,” the Apostle Paul says, “comes knowledge of sin” (Rom. 3:20). The law is like a mirror that exposes our sins.
- The law also pronounces a judgement on us as guilty sinners. Because of our disobedience to God, we deserve punishment, that punishment being death (Rom. 6:23).
- But the law also points us to Jesus Christ who kept the law on behalf of guilty sinners and died in their place, so that sinners who believe in him will be justified on the basis of his righteousness. “Wherefore the law was our schoolmaster to bring us unto Christ, that we might be justified by faith” (Gal. 3:24 KJV).
So, when used by the Holy Spirit, the law (1) convicts us of our sin, (2) condemns us, and (3) creates in us a sense of need for Christ who alone can redeem us from the curse of the law (Gal. 3:10).
3. In relation to sanctification, the law instructs us to live a holy life out of gratitude for what God has done for us in Christ (the didactic use of the law).
The Heidelberg Catechism, a reformed document published in 1563, primarily uses the law in this way. Divided into three main sections (guilt, grace, & gratitude), this catechism asks, “We have been delivered from our misery by God’s grace alone through Christ and not because we have earned it: why then must we still do good?” Answer: “To be sure, Christ has redeemed us by his blood. But we do good because Christ by his Spirit is also renewing us to be like himself, so that in all our living we may show that we are thankful to God for all he has done for us… And we do good so that we may be assured of our faith by its fruits… (Q&A 86)”
In other words, why do good works if we have not been saved by our good works? Or why obey the law if we have not been justified by our obedience to the law? Why? Because our obedience to the law shows that we have truly been justified by faith in Christ (James 2:17). Moreover, our obedience to the law is an expression of our gratitude to God for what he has done for us in the gospel. We love the Lord our God with all our heart and with all our soul and with all our mind and we love our neighbors as ourselves in response to the great gift of salvation that God has given to us.