The Third and Principal Use
It’s worth noting, as many have, that the Heidelberg Catechism included its exposition of the Law in the gratitude section and not in the guilt section. This choice reflects the widespread Reformation belief in the so-called third use of the law. The law is given (1) to restrain wickedness and (2) to show us our guilt and lead us to Christ. But, according to Calvin, the “third and principal use” of the law is as an instrument to learn God’s will. The law doesn’t just show us our sin so we might be drawn to Christ; it shows us how to live as those who belong to Christ.
In one sense Christians are no longer under the law. We are under grace (Rom. 6:14). We have been released from the law (Rom. 7:6) and its tutelage (Gal. 3). On the other hand, having been justified by faith, we uphold the law (Rom. 3:31). Even Christ recoiled at the idea of coming to abolish the law and the prophets (Matt. 5:17). Christians are free from the law in the sense that we are not under the curse of the law–Christ is the end of the law for righteousness to everyone who believes (Rom. 10:4)–nor is the law a nationalized covenant for us like it was for Israel. But the law in general, and the Ten Commandments in particular, still give us the principles which instruct us how to live.
The Ten Commandments were central to the ethics of the New Testament. Jesus repeated most of the second table of the law to the rich young man (Mark 10:17-22). The Apostle Paul repeated them too (Rom. 13:8-10) and used them as the basis for his moral instruction to Timothy (1 Tim. 1:8-11). The commandments are holy and righteous and good (Rom. 7:12). How could they be anything else? They are an expression of God’s character. If we do not love what God commands us to do, we do not love what God is like.
We obey the commandments, therefore, not in order to merit God’s favor but because we have already experienced his favor. The Decalogue was given to Israel after God delivered them from Egypt. The law was a response to redemption not a cause of it. In one sense, the law shows us our sin and leads us to the gospel. But in another sense, law ought to follow the gospel just as the giving of the Decalogue followed salvation from Egypt. We obey God’s words not because we cower under threat of judgment, but because we stand confidently with our Deliverer and gladly accept his good rule for our life.