There are two words that every Christian needs to know in order to rightly interpret the Scriptures and live the Christian life without confusion. These two words are Law and Gospel. They belong in everyone’s vocabulary for the Christian life and are the key to opening God’s Word.
The law is a word that comes to us from within, and it is written on everyone’s heart (Rom. 2:15). It was once written on stone tablets in Israel’s history, and in the history of man it is inscribed on the conscience. Everyone gets law, and everyone prescribes law to others.
When you ask a friend for some advice, the first words spoken are often words of doing. Do this. Don’t do that. The law brings no hope of relief but only tells us where we’ve gone wrong and what we need to do in order to make things right (Rom. 3:19–20). The law says, “Do this and live” (Lev. 18:5; Gal. 3:12).
It's not that the law is bad. In fact, the law itself is good because it comes from God and is a reflection of his good character. The apostle Paul even says, the "law is spiritual" (Rom. 7:14). So we know that the problem is not with the law, but the problem is with us.
As Paul concludes, although "the law is spiritual" but "I am of the flesh, sold under sin" (Rom. 7:14). We are bad—the law exposes our sin—and that's why the law becomes bad news for us.
The gospel is a word that comes to us from outside of us, and it has been revealed by God in his Christ. This word must be spoken, and it is the good news of what God has done in Christ to reconcile us to himself—to satisfy all of the demands of the law and to make atonement for all sins committed.
What the law required, Jesus Christ has accomplished. What the law demanded, Jesus has satisfied. The gospel says, “Believe this, and it is done already.” Jesus’ final words on the cross are appropriate to summarize the good news of the gospel: “It is finished!” (John 19:30).
Whenever you read a verse, you can immediately tell whether it is law or gospel by either the demands it makes upon you or the promise it offers you.
The law commands you to do something, or to stop doing something. The gospel, however, tells you what God has done for you, or what he will do for you. What separates the teaching of Christianity from every other world religion is that the Bible reveals to us how the law can never save us; only Jesus can.
No other religion tells us that God has done what we could not do for ourselves. No other religion offers us the gospel: the free grace of God in Jesus Christ. "Thanks be to God through Jesus Christ our Lord!" (Rom. 7:25).
I want to offer ten basic biblical truths that guide Christian responses on this question .