Law and gospel is the framework according to which a sermon should be constructed and preached. The sermon is not simply a publicly offered speech providing religious information or a lecture on Christian doctrine, though in some cases it might be just that and no more. Rather the sermon addresses the hearer so that he finds himself in the sermon as one condemned by God (law), but who in the next moment hears that he has been redeemed by that same God in Christ (gospel). Preaching extends the historical events of Israel and Christ’s life and their interpretation by the prophets into the lives of His people whom God desires to save. It addresses the unbeliever and believer in the same way, since the believer remains a sinner for as long as he lives (FC SD VI.7-8). The believer is caught in the despair brought on by his own sins, but then he hears God’s promises and by faith he possesses everything Christ by His death has won for him. What happened as a one-time historical act and then was written in the Scriptures by prophets and apostles is now proclaimed by preachers for the salvation of their hearers.
Law and gospel is a distinctively Lutheran principle for theology and for interpreting the Bible. Francis Pieper is right in his claim that only Lutheran theology centers in the gospel, as even many non-Lutherans acknowledge. Roman Catholics place the law after the gospel. The Reformed know the principle and interpret it differently, as is particularly evident in their definition of the third use of the law, as shown above, but even with this different understanding it is not at the center of their theology. Baptists show little interest in the topic. John Wesley, the founder of Methodism, found Luther’s distinction blasphemous. Where preachers of other Christian traditions preach law and gospel, they do not do it because it has been articulated for them by their theologians but because they have followed the Scriptures.
We have already noted that some Lutherans can articulate the distinction between the law and the gospel but many not be able to preach or practice it. Other Lutherans may know the distinction but have dismissed it as having no purpose in their preaching. Some non-Lutheran preachers may have no acquaintance with it. Preaching which uses the law as a motivation for Christian living or sanctification is a denial of the law-gospel principle. This happens among Lutherans when they hold that the third use of the law allows them to apply the strictures and threats of the law to Christians as they are believers. Interpreting the Scriptures by the law and the gospel does not mean that their content is fully exhumed and exhausted by this principle or that the principle itself comprises the entire biblical truth, a position advocated by Rudolph Bultmann in the last century and which was taken over into Lutheranism in America. For him Scriptures were true only insofar as they proclaimed forgiveness through the law and the gospel. His position was not unrelated to Barth’s in locating the revelation in the moment of faith. Law and gospel describe the saving purpose of the Scriptures, but the history of Israel and Jesus provide the historical substance through which faith is created. The Scriptures are documents intended for proclamation, but they are also historical accounts given first to Israel and then to the church. When the history of Jesus – especially His crucifixion and resurrection, in which redemption is enacted and on which justification is based – is denied or regarded as inconsequential, the law and the gospel can no longer perform their task in bringing the believer into God’s redemptive acts. Gospel is more than a proclamation of forgiveness, but finds its presupposition in the historical reality of Israel and Jesus. The law and the gospel are standards neither for judging the truthfulness of the Scriptures nor for setting down minimal doctrinal specifications, as if a person need believe only that he is both condemned and forgiven by God.
“Confessional Lutheran Dogmatics: Law and Gospel and The Means of Grace”, pages 60-61