Picture John now, in the middle of his hellfire and brimstone sermon, splashing around in the Jordan River, proclaiming to the crowds that the coming Messiah, "will baptize you with the Holy Spirit and fire!"
In other words, John was once again recognizing that He was not the Messiah. The One who was coming was greater, and He would have a greater baptism to offer. Through Christ a baptism with the Holy Spirit would come, but Christ would also bring with Him a baptism of fire— of judgment— a baptism of flaming judgment upon all those who refuse to worship Him.
John was not in the business of preaching light, feel-good messages. He preached the truth, regardless of its terror. John further proclaimed to the crowds concerning the Christ, saying, "His winnowing fork is in his hand, and he will clear his threshing floor and gather his wheat into the barn, but the chaff he will burn with unquenchable fire."
The crowds would have instantly connected with this illustration. At the end of the season, farmers would harvest their crop. But not everything they harvested was worth keeping. To get rid of the worthless, inedible parts of the gathered wheat (the chaff) farmers would toss their crops up into the air with a winnowing fork. All the chaff, which was lighter than the wheat, would blow to the side, but the wheat would fall back down in its place.
That is the image John is after. Christ will find all the hypocrites. When He tosses up the mass of humanity, all the hypocrites will be blown toward their destruction. And what kind of destruction is it? John tells us that they will be burned with fire. That alone would be terrifying, but John tells us more. They will not be burned merely with fire, but with an unquenchable fire.
The penalty for rebellion against God is serious. It is not a momentary thing. You aren't just burned at the stake for five minutes until you suffocate and your body disintegrates. No, it's far worse. This is an unquenchable fire, a fire that cannot be put out.
Oh let us worship and praise the Christ whom John exalts in his preaching! Think for a moment of what Christ bore for you, oh believer! He bore an unquenchable fire, a fire that would be upon you forever and ever. Let such awful thoughts drive you closer to Him, to honor Him more, and to see the greatness of His love.