In a series of recent posts I have discussed the fact that while Paul's letters remains fixed firmly in the Gospel, they never cease to speak about how Christians will live in the world - what is often described under the theological heading "sanctification" ("Would Paul wants pastors to preach and teach about good works"; http://surburg.blogspot.com/2013/03/would-paul-want-pastors-to-preach-and.html; "Are there 'good Christians' and are they role models for imitation?"; http://surburg.blogspot.com/2013/04/marks-thoughts-are-there-good.html; "Some Lutherans love Romans 7 and don't seem to realize that Paul wrote Romans 8"; http://surburg.blogspot.com/2013/04/marks-thoughts-some-lutherans-love.html; "Paul and love - evidence for deepening and growth in sanctification"; http://surburg.blogspot.com/2013/04/marks-thoughts-paul-and-love-evidence.html). I have maintained that if the apostle spoke this way in his letters, then there needs to be a place for it in Lutheran preaching and teaching as well.
No two texts are the same and no two Sundays are the same in the life of a congregation. Because of these factors, as the pastor proclaims a text to his congregation no two sermons are going to be the same. The emphasis in sermons will vary over time. However, the discussion of living as Christians and how this flows forth from baptism and faith in Christ should be regular elements in our preaching - just as they are for the New Testament. When texts readily lend themselves to this - as they often do - we should take advantage of this opportunity.
It is easy for the discussion of the topic of sanctification to get lost in theological generalities. As an exegete, my concern is that we always return to the specific biblical and Confessional texts so that we consider what they actually say. In the same way, it is helpful to consider what specific examples of preaching look like when talking about "sanctification." It is easy to create a straw man argument by pointing to the wost excesses of American evangelicalism. However, to speak of a deepening in sanctification in no way necessitates the loss of a Gospel focus on Christ's saving work that is grounded in his gifts of the Means of Grace.
Below is the link to my sermon for the Third Sunday of Easter, Misercordia Domini. It is a sermon based on 1 Peter 2:21-25. Like Paul, Peter's first letter is grounded in the Gospel (and especially baptism) and at the same time it contains a strong emphasis on how Christians will live in the world. Not every sermon is like this. But I believe that if we never or only rarely speak in this way, then it becomes difficult to explain why we don't reflect the practice of the apostles.