For the next three Sundays, the Gospel readings put John the Baptist in the spotlight. This week it is his proclamation. Next week it is his question. The following week it is his prenatal gymnastic reaction. The Baptizer clearly does not relish the attention, for he repeatedly directs people away from himself (see verses 15-18). This makes him a useful guide through the season of Advent.
A challenge to preaching sermons from John the Baptist texts is he is not in the same kerygmatic boat as contemporary Christian preachers. As Andy Bartelt points out, John is the caboose on the prophetic train. Like Isaiah, Malachi, and the prophets of old, John preaches from the wilderness to prepare the people for the coming of the Lord. Preachers today also prepare people for the Lord’s coming, and the wilderness is an apt metaphor for life in this world. But Jesus’ second coming is not His first. This matters for a sermon on this text, because John was not speaking to contemporary hearers. Preachers today, therefore, should not imagine themselves in the exact same sandals as the camel-hair-wearing, locust-eating prophet. Neither should they bluntly identify their hearers as a “brood of vipers.” Baptized and believing, post-resurrection Christians are not John’s hearers in the text.
Yet, people still need to be prepared. That is the point of Advent and the job of the preacher. To do this, the sermon might focus on verse 8: “Bear fruit in keeping with repentance” (μετανοίας). This was the heart of John’s message, but for the crowds in the text it remained too abstract. They needed something more concrete, which is why they asked him what this fruitful repentance looks like: “What shall we do?” (Notice that Luke records three different groups of people asking this same question three distinct times.) John’s answers show that bearing fruit in keeping with repentance takes concrete shape based on the individual’s situation. For soldiers it involves not extorting and being content with wages. For tax collectors it involves honest collecting. For the crowds it involves generous sharing of food and tunics.
He was not speaking to Christians, but John’s call to fruitful repentance remains an important message today. The second coming of Jesus is always imminent and the influences of the sinful flesh and the fallen world on the Christian life are constant. Thus, the call to repent is always a central feature in the proclamation of the Gospel. But for this same reason, it can easily become routine and mechanical. That is where John’s concrete description of vocation-specific fruit offers a way to preach a specific message this Sunday. John reminds us repentance involves more than guilt and regret over the past. More broadly, it includes turning away from a life that does not conform to the reign of God and turning towards an active life of humble and loving service to others.
*This would be a good week to revisit article XII of the Augsburg Confession and Apology on repentance. Notice especially how the Apology talks about fruitful repentance in paragraphs 28 and 45. Strictly speaking, repentance includes only sorrow over sin and trust in the promise of God in Christ. But it is also appropriate to speak of repentance in a way that includes its fruit and new life.
Perhaps this week’s sermon could organize itself around Luke’s thrice-repeated question. Instead of soldiers, tax collectors, and tunic wearing crowds, the preacher could identify three distinct vocations represented in the local congregation. Which industries/stations are common in your congregation’s context? What temptations are specific to these vocations? What opportunities for fruitful living present themselves in these contexts? (If you don’t know the answers to these questions, ask members of your congregation! They will be happy to help you.)
The sermon could then begin by creatively imagining how soldiers, tax collectors, and first-century crowds would have heard John’s message of fruitful repentance. Imagine them asking their questions with genuine curiosity and a heartfelt desire to be prepared. You might even imagine what the next day or week or month would have looked like for them as they try to put John’s message into practice. After this the preacher could return to the 21st century and imagine their three contemporary groups asking the same question. This part of the sermon could have the feel of a conversation between a pastor and these three groups. Each conversation would include fresh calls to repentance and concrete examples of living the new life in expectation of Jesus’ return. The preacher would want to help other hearers (who are not in those three vocations) make appropriate application for their lives, but this can be done easily by inviting all the hearers to connect the dots which the sermon did not specifically address.
Because preparation for Jesus’ return depends on faith in His promises, His promises must be clearly proclaimed. The sermon could do this by including a fourth questioner. The preacher could imagine a conversation between the Father and Jesus. Jesus might wonder out loud, “What shall I do? Shall I smite those greedy soldiers and tax collectors? Shall I reply to the selfish crowds with my own selfishness?” The answer is, “No,” of course. Rev. John Bell’s poem could be part of the Gospel answer:
Light looked down and saw the darkness. ‘I will go there’, said Light
Peace looked down and saw war. ‘I will go there’, said Peace. Love looked down and saw hatred. ‘I will go there’, said Love.
the Lord of Light,
the Prince of Peace
the King of Love
came down and crept in beside us. 
Concordia Theology: Various resourced to help you in preaching Luke 3:1-20.
Lectionary Podcast: Dr. Walter A Maier III of Concordia Theological Seminary, Ft. Wayne, IN, offers guidance through Luke 3:1-20