The great Protestant reformer, Martin Luther, famously dichotomized the Word of God into “gospel” and “law.” Luther was not the first to distinguish between gospel and law, of course. The Apostle Paul gets that honor. But Luther made the distinction a bit more sharply than anyone else before him. For Luther gospel and law are two different ways that the Word of God comes to us: the gospel is discourse about what God does for us and in us, specifically what he does in Jesus Christ. The law, on the other hand, is discourse about what we do.
Notice that the distinction is not about different parts of the Scriptures—like the gospel is found in Matthew, Mark, Luke and John, and the law is in the books of Moses. No, for Luther, the gospel can be found all over the scriptures, and so can the law. What we have instead is a helpful little tool to distinguish how God is speaking to us when he is. So, in the prologue to the Ten Commandments, when God says “I am the Lord your God who brought you out of the land of Egypt out of the house of slavery” (Exodus 20:2)—that’s the gospel, right there in the Law of Moses. It’s about what God has done for us. On the other hand, when Jesus commands us to “love the Lord your God with all your heart and with all your soul and with all your mind and with all your strength and love your neighbor as yourself” (Luke 10:27)—that’s law, even though it’s found in the Gospels.
Both gospel and law are equally the word of God, and so both are equally good. But they serve different purposes. To provide an analogy, I speak to my child differently when I want to tell him that I love him than when I want to tell him not to stick a screwdriver in the outlet. In both instances what is being spoken is equally my word. And, in a way, each communicates the same thing: that I love my son and want what’s best for him. But I speak differently because I want to elicit a different response. In the one instance I want my child to know that his father loves him, in the other I want to stop doing what he’s doing. In the same way, both gospel and law are God’s word to us. And they’re both good! Really, they’re saying the same thing: that our Father loves us and wants what’s best for us. But they are two different genres of discourse, designed to elicit different responses. The proper response to God’s law is obedience. The proper response to the gospel is faith. That’s because the gospel is really a kind of promise—a promise that God loves you and has acted or will act for your good. There’s nothing more we can do with a promise, except just to believe it. And that’s what faith is: trusting in God’s Word of promise to us.
This is where Luther’s distinction becomes helpful. We can always tell whether we’re hearing gospel or law by answering the question: “What am I supposed to do with this statement?” If you are supposed to do something—pray a prayer, walk down an aisle, apply it to your life, etc.—that’s the law. Remember that the law is God’s word, too. The law cannot save us, but it is good. It’s God’s way of telling us what to do because he loves us and wants what’s best for us, (like me telling my son not to stick a screwdriver in the outlet). But if you hear a statement about how God has acted on your behalf and there’s nothing you can do with the statement except to believe it, that’s probably the gospel. Think about what that means. If I tell you “what you must do to be saved”—that’s law. I’m telling you something you must do—that’s the definition of law, and it cannot save you. If you want to be saved, then we can’t talk about what you do. Instead, we’ll have to hear the gospel—the story about what God does in Jesus Christ for us and for our salvation. He came down from heaven and was made man. He was crucified, died and was buried. On the third day he rose again. He ascended into heaven. He will come again in glory, and his kingdom will have no end. That’s the story that can save us. That’s what God has done for us in Jesus Christ. That’s the gospel—believe it!