The passage
      v1. Luke, in the style of a Greek historian, dates the preaching ministry of John and the baptism of Jesus, by cross referencing significant personages of the time. His dating is around 27-29AD.
      v2. Although the Romans removed Annas in 14AD, he continued to exercise power while his son-in-law, Caiaphas, was High Priest. The wilderness/desert is where we meet God and so it is where John receives his call from God.
      v3. Only a Gentile convert to Judaism would be baptized (a sign of regeneration), but John demands that Abraham's children must now be baptized. It was as if Israel had reached the river Jordan and must again cross the river to enter the promised land. So, John preached a message of repentance, a repentance which had but one aim, the forgiveness of sins. Baptism, water immersion, serves as the outward expression of this repentance, while at the same time illustrating the cleansing of forgiveness soon to be realized in the coming messiah.
      v4-6. Luke now quotes Isaiah 40:3ff. John's task is to prepare the way for the coming messiah. The Exodus journey of the messiah and his people to the promised land is made clear and straight by John's call to repentance. Those who heed the call will gain the long-hoped-for messianic deliverance.
      v7. John sees the "multitude" coming toward him and questions their commitment. Although the description, "snakes" (children of the Devil), particularly applies to the Pharisees and Sadducees, John suspects that this crowd, which seeks to escape the day of judgment through baptism, is responding to his preaching at a superficial level.
      v8-9. For John, baptism is an outward manifestation of repentance - the symbolic expression of a genuine cry for mercy. Genuine repentance exhibits an attitude of neighborly-love and serves as the mark of the new Israel.
      v10-11. Heartfelt repentance accesses the mercy of God, which mercy prompts mercy. Here, radical generosity.
      v12-13. The profession of tax collector is not sinful in itself, but in the Roman provinces it was often corrupt, a form of legalized extortion.
      v14. Neither is policing a sinful profession, but again, it is open to corruption. The solders referred to here are most likely Jews, members of Herod's local police.
      v15. Messianic expectation is high and so many in the crowd wonder whether John is the messiah.
      v16. John indicates that his role is preparatory; he performs water baptism as a sign of repentance in preparation for the coming messiah. The messiah, who is about to inaugurate the long-expected kingdom, will baptize (in the sense of immerse or overwhelm) with, or in, the Holy Spirit and fire. Those who follow the coming messiah will be washed clean with his regenerating Spirit, but will also face the fire of persecution, of tribulation.
      v17. Luke reminds us that the coming judgment is central to John's gospel message. The good news of a coming messiah has its bad-news side.
      v18. Luke explains that the above is a summary of John's gospel preaching.
      v19-20. Luke then summarizes John's run-in with Herod and so reminds us that John prepares the way for Jesus in his suffering, as well as in his preaching.

True repentance
      John the Baptist's ministry has a threefold purpose:
        i] He prepares the way for the coming of the messiah by calling on the people of Israel to repent in preparation for the messiah's arrival;
        ii] He explains the nature of the messiah's mission. The messiah will baptize with the Holy Spirit and fire;
        iii] He witnesses to the messiah as one "more powerful than I."
      It is interesting how Luke tells us that John was "preaching a baptism of repentance for the forgiveness of sins." Baptism is not so much done, as preached or proclaimed. Luke also tells us that the substance of this proclamation is the gospel, he "gospelled them." The gospel proclaims that in the face of the coming day of judgment, forgiveness, and thus, acceptance by God of the sinner, is available to all those who repent.
      On the surface, it seems that repentance is an act of turning away from self toward a life of neighborly care. Yet, the substance of repentance is certainly not good works. Repentance is a turning to God for mercy and acceptance. It is something the sinner does in search of salvation. Repentance is the cry: "Lord have mercy on me a sinner." Only then, having received God's mercy, can we respond by showing mercy.

2b
      egeneto epi "[the Word of God] came to [John]" - came upon, on, over, to. Used in the LXX of divine inspiration; John's message is God's message. "God spoke to Zechariah's son John", CEV.
      en th/ erhmw/ (oV) "in the desert" - A place of reflection, retreat and revelation. Probably for John, the wilderness is the area north west of the Dead sea, leading into the Jordan valley.

v3
      eiV pasan "into all" - to, into all/every. John's ministry covered the whole of Jordan; "he went all over the Jordan valley", REB.
      khrusswn (khrussw) pres. part. "preaching" - communicating, proclaiming. The participle serves to express manner, how John came; he came preaching. The present tense indicating ongoing action. The sense is of authoritative communication, heralding, proclaiming openly, and in the NT. of proclaiming the gospel. Note, the following clause defines what John preached.
      baptisma (a atoV) "a baptism" - immersion, overwhelmed. The word, "immersion", is used both figuratively and literally. It is often used to describe water immersion, but also overwhelmed in/by/with the Spirit, tribulation ("fire") and teaching ("into the Name"). Here it is most likely that water immersion is intended, although it is strange to say that John preached immersion. Presumably the stress is on the substance of the immersion, that which it represents, namely, repentance. So, John preached a message concerning repentance for the forgiveness of sins, which repentance was expressed outwardly in water baptism. It is also argued that the sign of water baptism illustrates cleansing. This does seem likely since Jesus' baptism with the Spirit for regenerative cleansing is prefigured in John's baptism with water.
      metanoiaV (a) gen. "repentance" - The Hebrew origins of the word obviously dictate its meaning. It involves a turning back / returning to God, rather than a mere expression of sorrow. Obviously, good deeds, in the sense of the fruit of repentance, follow, but such deeds are not a necessary component of the inward act of repentance. Forgiveness does not rest on the deeds (fruit), but on a turning toward God, which turning taps into God's grace.
      eiV "for" - into, to, for. A causal sense has been argued, as has result, but purpose seems best. "John preached a message of repentance, which repentance had as it purpose, the forgiveness of sins."

v4
      wJV gegraptai (grafw) perf. pas. "as it is written" - Usual formula for an authoritative quote from scripture.
      fwnh (h) "a voice" - a voice, sound. Although without an article, it may be understood as definite due to its association with the genitive participle "calling." Following the MT the verb to-be may be assumed; "a voice is crying." "Hark! someone is shouting", Phillips.
      thn oJdon (oV) "the way" - Luke sees John fulfilling Isaiah 40:3-5 as the one who prepares a roadway through the desert, an expressway ready for the journey of messiah to Jerusalem.

v5
      plhrwqhsetai (plhrow) fut. pas. "shall be filled in" - will be filled. It is possible to take the future tense here as an imperative, eg. "fill up every valley", CEV.
      ta skolia adj. "the crooked roads" - the crooked, twisted. The adjective as a noun. Possibly not an existing road, but a place too rough and steep to normally take a road. "The crooked places must become straight roads", Williams.
      estai (eimi) fut. "shall become" - Note the position of the verb to-be before the subject serving to emphasize the reality of what will be.

v6
      sarx (x koV) "mankind" - flesh. Used here for the Hebrew "living thing", meaning "humanity", NJB.
      to swthrion adj. "salvation" - the salvation. Note how Luke has replaced "glory" with "salvation" from the original. Of course, God's glory is manifested in his salvation of broken humanity.
      tou qeou gen. "God's [salvation]" - [the salvation] of God. Obviously a subjective genitive and this should be made clear; "all humanity will witness God's work of salvation."

v7
      oun "-" - therefore. Resumptive.
      elegen (legw) imperf. "John said" - he was saying. The imperfect possibly reiterative, so Nolland, although often the imperfect in Luke is simply a literary device used to express a vivid ongoing scene, so Bock. "He would say", Nolland.
      toiV ocloiV (oV) dat. "to the crowds" - In Matthew and Mark, John actually addresses the religious leaders, so it is interesting that these rather harsh words are addressed to the people in general.
      baptisqhnai (baptizw) aor. pas. inf. "to be baptized" - to be immersed. The infinitive expressing purpose, why the crowd came out to John.
      gennhmata (a atoV) "brood" - offspring, produce, children/sons of. Simply, "you snakes", CEV.
      ecidnwn (a) gen. "of vipers" - snakes, reptiles. Descriptive genitive. Possibly an allusion to the Devil. These Israelites, who should be sons of God, are sons of the Devil, ie. lost and facing judgment.
      uJpedeixen (uJpodeiknumi) aor. "warned" - showed, informed, pointed out, told. With an infinitive, usually "warned", although the more general "informed" fits better. Although the sense is debatable, it seems likely that John is reacting to a superficial response to his preaching (something we would never react to today!), so he indirectly questions the level of commitment of those seeking baptism, cf. v8. Where indeed did they get the idea that ritual immersion would enable them to escape the day of judgment? "Do you really understand what my baptism is all about?" Bock.
      thV melloushV orghV "the coming wrath" - Referring to the day of judgment, obviously an important element in John's preaching.

v8
      As noted above, the fruit of repentance is not an integral element of repentance. Repentance entails a turning to God for mercy, which mercy prompts a renewed life-style. John rightly identifies continued societal evils as evidence that the crowd's repentance is not genuine.
      oun "-" - therefore. possibly inferential; "if you want to be saved, then ..." TH., although a consequential sense is more likely, "then", Nolland. "Now produce fruits that answer to your repentance", Moffatt.
      poihsate (poiew) aor. imp. "produce" - make, do. A strange expression, possibly a Hebraism. Often taken in the sense of "produce" or "prove", but best "let your lives then prove your change of heart", Weymouth.
      mh arxhsqe (arcw) aor. subj. "do not begin [to say]" - may begin. The negated subjunctive expressing a prohibition, "don't let the thought enter your minds that"; "do not even begin to say", Williams.
      ek twn liqwn "from these stones" - The allusion is unclear. Possibly alluding to Isaiah 51:1-2 where Abraham is referred to as a rock from which God cuts the stones who seek him. John's point is that "placement into blessing is not a matter of election through mere biology", Bock.

v9
      kai "-" - and. Here a sentence adverb, "it is even the case that", Nolland. hdh adv. "already" - now, already. Emphasizing the urgent nature of John's message due to impending judgment.
      proV + acc. "at" - to [to the root of the trees is laid]. The sense is of movement toward, but with "laid" implies movement having come to rest. So, the aiming stroke is indicated where the axe first touches the wood prior to the first stroke. An image of judgment.
      oun "and" - so, therefore, consequently, accordingly, then, so then. Here probably expressing result; "so that ever tree that does not produce good fruit", Weymouth.
      mh poioun (poiew) pres. part. "does not produce" - not making. The present tense, as with "cut down", is gnomic, expressing a timeless fact. The negated participle possibly forms a conditional clause; "if a tree does not produce good fruit, it is cut down ..."
      ekkoptetai (ekkoptw) pres. "will be cut down" - is cut down. Futuristic present tense.

v10
      poihswmen (poiew) aor. subj. "should we do" - Deliberative subjunctive. "What is the product that reflects true repentance?" Bock.
      oun "then" - therefore. "Given what you have just said, what should we do."
      ephrwtwn (ephrwtaw) imperf. "[the crowd] asked" - [the crowds] were questioning [him saying]. Probably an inceptive imperfect, "they began to question him."

v11
      metadotw (metadidwmi) aor. imp. "should share with" - let him share. Note how John defines the fruit of repentance in the terms of personal radical generosity. He neither calls for the abandonment of society (communalism), nor the reformation of society (political activism, etc.). This is not to say that either abandonment or involvement are necessarily wrong in themselves, just that mercy (generosity, kindness) is the primary fruit of repentance.

v12
      telwnai (hV ou) "tax collectors" - Local duty collectors in the service of the Roman Government. They often used their franchise, under the authority of the Roman government, to collect duties on the sale and transport of goods, over and above a nominal commission.
      baptisqhnai (baptizw) aor. pas. inf. "to be baptized" - The infinitive used to express purpose.
      poihswmen (poiew) aor. subj. "[what] should we do?" - Deliberative subjunctive. "Master, what are we to do?" Phillips.

v13
      mhden .... prassete (prassw) pres. imp. "don't collect" - do. "Exact no more than the rate fixed", Barclay.
      para + acc. "[any more] than" - beside. Here taking the force of a comparative genitive, TH.
      to diatetagmenon (diatassw) perf. pas. part. "required" - assign, arrange, demand. The participle functioning as a substantive; "fixed rate", Moffatt.

v14
      strateuomenoi (strateuw) pres. part. "some soldiers" - serving as a soldier. Either Jewish mercenaries in Roman service, or members of Herod Antipas' guard. "Police", Nolland.
      mhdena diaseishte (diaseiw) aor. subj. "don't extort money" - shake, shake down. "Don't extort by violence."
      mhde sukofanthshte (sukofantew) aor. subj. "don't accuse people falsely" - slander, cheat. Probably, "don't seek bribes."

v15
      prosdokwntoV tou laou "The people were waiting expectantly" - the people being expectant. The participle with the noun, both being genitive, = a genitive absolute, usually forming a temporal clause; "while the people were in suspense", Williams. Yet, a consequential clause seems more likely. The sense is that the crowd (Nolland suggests that "the people" = "the people of Israel", not just "the crowd", although the present audience seems best), which has come out to John, is now filled with messianic fervor due to his preaching, and therefore needs instruction; "As all this aroused people's expectations", Goodspeed.
      dialogizomenwn (dialogizomai) gen. pres. part. "were [all] wondering" - wondering, discussing, reasoning [everyone]. Again, a genitive absolute formed with the gen. "everyone." Possibly temporal, "when they were all debating in their minds", Barclay, but see above.
      en taiV kardiaiV autwn "in their hearts" - "All were reflecting fully on the matter", Bock.
      mhpote "might" - perhaps, lest. Possibly expecting the negative, ie. the people knew that John was not the messiah, but more likely expressing doubt, particularly with the optative of the verb to-be. "Perhaps he could be the messiah."
      oJ cristoV (oV) "the Christ" - the messiah. Properly rendered "the Messiah", Barclay.

v16
      pasin "[John answered them] all" - "All Israel", so Nolland, but surely, given the context, John is addressing all in the crowd, not just those being baptized. None-the-less, the words do apply to all Israel, as they do to all humanity.
      egw "I" - Emphatic.
      baptizw pres. "I baptize" - Present tense = ongoing action; "I am baptizing with water", TH.
      uJdati (wr atoV) dat. "with water" - The dative is probably instrumental, but the locative "in" is possible. The position is emphatic, so, "only with water."
      oJ iscuroteroV comp. adj. "one more powerful" - the one stronger. "One mightier than I", NAB.
      iJkanoV adj. "[I am not] worthy" - significant, able, worthy, adequate, competent.
      lusai (luw) aor. inf. "to untie" - to loose. Epexegetic infinitive explaining what John is not worthy to do.
      autoV "he" - Emphatic.
      en + dat. "with [the Holy Spirit and fire]" - in, with, by. Probably instrumental, "with", although locative, "in", is possible; "He will baptize you in the Holy Spirit and in fire", Williams.
      pneumati aJgiw/ kai puri "[with] the Holy Spirit and [with] fire" - The meaning of these words has prompted endless debate. A singular sense is possible, eg. "the purging (cleansing) Spirit", "the fire of the Holy Spirit", Phillips, or "the holy fire of judgment", but it is likely that the messiah "immerses / overwhelms" with both the Spirit (cleansing through regeneration) and fire (tribulation). This line of interpretation can be traced back to Origin, although it is not adopted by most modern commentators. Fitzmyer argues that the two-baptisms position defies good grammar.

v17
      This verse may serve to explain baptism with Spirit and fire, or even just baptism with fire, but is more likely a separate, but central, element in John's gospel message, namely, "the day of judgment is at hand."
      diakaqarai (diakaqairw) aor. inf. "to clear" - to clean out, thoroughly clean. Infinitive expressing purpose, "in order to cleanse."
      sunagagein (sunagw) aor. inf. "to gather" - to gather, bring together, call together. The infinitive again expressing purpose, "in order to gather."
      katakausei (katakaiw) fut. "he will burn up" - will burn up, consume.
      puri asbestw/ dat. "with unquenchable fire" - with fire inextinguishable. Meaning a fire that can't be put out, alluding to the rubbish dump outside Jerusalem that was constantly burning, which image illustrates the horror of judgment, although not necessarily "eternal" judgment, cf. Isa.34:10, 66:24, ..... (The notion of the ongoing punishment of the wicked is questionable). The dative is obviously instrumental, "with". "He will burn the chaff with fire that nothing can put out", Barclay.

v18
      men oun kai "and" - and indeed therefore. Serving to introduce a conclusion / summary. "Now also", Bock.
      polla .... eJtera "many other words" - many other [exhorting]. "Word's" assumed, although possibly "ways", cf. REB etc. The point is that the previous verses is but a summary of John's preaching. "These and many other things John said to the people as he exhorted them and announced the good news", Phillips.
      parakalwn (parakalew) pres. part. "John exhorted" - exhorting, urging, admonishing. Nolland suggests "to admonish", reflecting John's stern message. Possibly the "exhorting" is one with "preaching the good news", eg. "In many different ways John preached the good news to the people", CEV.
      euhggelizeto (euaggelizw) imperf. "preached the good news" - he was proclaiming. Usually a technical term referring to gospel preaching, so "evangelizing", but possibly just in the sense of communicating, "he spoke his message to the people", Moffatt.

v19
      de "but" - With men in the previous verse a contrast may be intended: "now on the one hand ....... but on the other hand ....."
      elegcomenoV (elegcw) pres. pas. part. "when John rebuked" - being reproved, convicted, exposed, censured. Temporal participle, so NIV, but possibly causal; "But Herod the governor, because he was repeatedly reproved by John for (marrying / "for his relations with", NJB) Herodias his brother's wife, and for all the wicked deeds that Herod had done", Williams.
      peri + gen. "because of" - concerning, about [Herodias].
      tou adelfou (oV) "brother's" - of the brother. Herodias was initially married to Herod, son of Herod the Great and Mariamne, but then married his younger brother, Herod Antipas, son of Herod the Great and his second wife, Malthake. kai peri pantwn "and all" - and concerning all things. "And for all the other crimes he had committed, v20, added a further crime to all the rest by shutting John up in prison", NJB.
      wJn gen. "-" - [and about all sins] which / that [Herod did]. An example of the direct attraction of the relative pronoun into the case of its antecedent, here "all". The case is determined by its function in the clause, so accusative might have been expected, but through attraction it is genitive. "All the wicked deeds that he had done", Weymouth.