The reading from Luke for this week follows on the heels of the summary of John's preaching of a "baptism of repentance for the forgiveness of sins," and the claim that his proclamation, which sets the table for the arrival of Jesus, was what Isaiah promised centuries prior.
John's preaching is harsh and perhaps surprising; it is jarring, particularly as an approach to the Christmas season; and it is challenging. His preaching of repentance is a direct assault on human living that in any way ignores the appropriate orientation of the believer (any believer) towards her neighbor.
Unique to Luke's account of the Baptizer's ministry is the response of the crowds (compare Matthew 3:1-12; Mark 1:1-8; John 1:19-28), a point to which I return below.
"You Brood of Vipers" as Sermon Intro
A lot of preachers begin their sermons with what is essentially a liturgical formula: Grace to you and peace from God our Father and the Lord Jesus Christ, to which an "Amen" from the congregation is, if not expected, at least accepted.
Others begin with: May the words of my mouth and the meditation of my heart be acceptable to you, O LORD, my rock and my redeemer (Psalm 19:14, which is actually the end of something and not a beginning, but that's OK), which is an invitation into the shared experience that good preaching is. Others still may open with: Peace...the Lord...God (etc.) be with you, which invites an "Also with you."
John starts a little differently. He opens his homily on repentance with a broadside: You brood of vipers! What this is meant to invite, who knows, but John goes on, asking why they are even listening and who they think they are, with the answer clearly being, "Not all that." John's homiletical approach -- at least his introduction -- was, no doubt, effective; though I'm not sure I would recommend it. If you try the full-on "brood of vipers" approach let me know; I'd like to come and listen...and watch to see how "the crowds" respond.
One thing is certain in John's case: his audience knew where they stood with the preacher. John asks them a pointed question: Who told you to flee from God's wrath? Reminiscent of God's "Who told you you were naked?" the question is rhetorical, serving to emphasize both John's accusation (You are vipers!) and John's challenge (Bear fruits worthy of repentance!). John then presses the case, telling them that their ethnic and religious heritage, based on Abraham is meaningless.
We have a tendency, I think, to skip past this part of the text a little too quickly, so let us be clear: THIS IS HUGE. One of the central elements of the Old Testament covenant is the generational promise, which begins with Abraham, continues with Isaac and Jacob, and is extended through them to all of their descendants (cf. Exodus 3:6; Jeremiah 33:26). But John says that this promise is meaningless, apart from repentance. In other words, claiming promise of Abraham without the faith of Abraham simply doesn't work. John is changing the game, and his preaching challenges his hearers to get into it.
The claim that John makes about the descendants of Abraham is striking, and its application to a modern congregation or context can be as well. If God is able to raise up children to Abraham from stones, what then does that make us? Images of hardened hearts, the reality that God's chosen are all-too-often faithless people, the chosen-ness of sinners, all rush to mind (mine at least) when thinking about the "children of Abraham." We who have come to believe in the one who is more powerful than John are those newborn children (cf. Paul in Romans 4:13-25; Ephesians 3:6-7; etc.).
What John is doing in Luke is radical in a sense; he redefines to a large degree what it means to be a child of Abraham, including all who believe. But notice also that John does not reject Abraham's ethnic descendants out of hand or absolutely. This is no supersessionist claim. Rather all are called to repent, to bear fruits worthy of repentance, and to believe.
The Recurring Question of the Crowd: What Then Should We Do?
It must also be insisted that John's message is not simply a call to belief or trust. John challenges his hearers to right relationships not just with God, but with their neighbors as well.
Following his bombastic opening, the crowds respond to John's preaching. The nature of that response is unique to Luke's account. The "crowds" as a whole, then (even) the tax collectors specifically, and finally the soldiers each ask, "What then shall we do?"
John responds to each reiteration of this question by offering specific action that equates to "fruits worthy of repentance." To the crowds as a whole, John says: If you have more than you need, whether in terms of food or clothing, you must share. To the tax collectors, who were often guilty of adding a little extra taxation on the top of regional and Roman taxes, John says: Stop stealing from your neighbors. And to the soldiers John says: No more using your power to take advantage of simple citizens. No hoarding, no skimming, no extortion.
Broadly speaking, then, John's action-oriented fruits of repentance have to do with depriving our neighbor of what they need. Repentance here is not just (or perhaps even primarily) about the dialectic of faith and sin; rather it is about how we are living out the love of our neighbor.
The question which John's advent, John's preaching, and by extension our own, encourage us to ask is just this: "What, then, should we do?" How shall we respond to the Advent of the Messiah, which our preaching hails? What are the fruits of repentance, which we might bear? How can we meet the promise of the season, with real, meaningful expectation (cf. Luke 3:15)?