Dear brothers and sisters in Christ,
What does God say about all these commandments?
He says, "I, the Lord your God, am a jealous God, punishing the children for the sin of the fathers to the third and fourth generation of those who hate Me, but showing love to a thousand generation of those who love Me and keep My commandments." (Ex. 20:5-6).
What does this mean?
God threatens to punish all who break these commandments. Therefore, we should fear His wrath and not do anything against them. But He promises grace and every blessing to all who keep these commandments. Therefore, we should also love and trust in Him and gladly do what He commands.
From Concordia: A Reader's Edition of the Book of Concord, a helpful summary of Luther's thoughts from the Large Catechism:
The Ten Commandments always accuse. That is their chief use. They also serve as a rough curb against gross outbreaks of sin. But they also function as the "true fountain" from which all good works must spring. We never have to try to invent or create works to do that are pleasing to God or go beyond what He has given us. In these Ten Commandments we have the guide we need to understand what truly pleases God. Some of Luther's most powerful remarks about the difference between God's Ten Commandments and man-made Church rules are found here. Luther thunders against the pomposity and false teaching that certain "Church works" are better in God's eyes than the simple, humble, lowly works of common life, such as a young girl taking care of a little child. He provides a brief summary of the commandments and gain shows how the First Commandment is the fountain for all the rest. God has given us a great treasury by giving us the Ten Commandments.
We can see clearly in this summary statement the three uses (or functions) of the Law:
- Curb: "They also serve as a rough curb against gross outbreaks of sin."
- Mirror: "The Ten Commandments always accuse. That is their chief use."
- Guide: "But they also serve as the 'true fountain' from which all good works must spring."
While the first two functions are common to all people, Christian or not, as the Law of God is written on our hearts (Rom. 2:15; 2 Cor. 3:2-3), the third use is unique to Christians. For the Christian, who is in Christ, the Ten Commandments become the answer to the question: "Now what." In other words, while the Law serves to show our sin, it also serves to show us how to live. But it is still Law.
Today preachers confuse this third use of the Law with Gospel. They throw in a sentence at the end of the sermon that says, "So go and do likewise!" While true, this is not Gospel, for the Gospel is about God's actions, not the Christian's.
The Law binds, but the Gospel frees--always,--because the Gospel always declares God's gracious promises to you in Christ Jesus. Amen.