In a previous blog post (HERE), I described the baptism of the Holy Spirit or the Messiah’s baptism as referred to by John (Luke 3:16-17). Nevertheless, John describes the Messiah’s baptism as one “with the Holy Spirit and fire” (Luke 3:16; cf. Matthew 3:11). That is, it seems John referred to a single baptism or an immersion in both the Holy Spirit and fire. Some have understood John to mean Jesus would baptize his disciples with the Holy Spirit and the world (or those who reject him) with fire, but I don’t think John meant that at all. In Matthew’s account (Matthew 3:11) the single preposition en (G1722) is used for both the Holy Spirit and fire, indicating a single baptism.
Luke illustrates the work of Christ by comparing it to that of a husbandman, who uses a fan or ‘winnowing fork’ (or shovel). It had three or four prongs at one end and a 3-4 foot handle on the other. The husbandman would dig into the grain and cast it into the air. The wind would take away the light chaff while the heavy grain would fall to the threshing floor. In this manner the valuable grain was separated from the useless chaff. The fan or winnowing fork in the hand of Christ is the word of God. Through it he separates the good seed from the chaff. (John 15:3; cf. 13:10; 17:17; Ephesians 5:26; 1Peter 1:22).
The Scriptures tell us that God is a consuming fire (Deuteronomy 4:24), meaning he brings judgment, but more than this he is a refiner’s fire (Malachi 3:2-3) that purifies his people. Certainly, some will not be able to endure the fire and fall away (cf. Matthew 13:5-6, 20-21), but the good seed will endure. The word of God brings persecution to those who receive it. Only those who embrace the truth with all their hearts are able to endure the refiner’s fire, and their works are purified into gold, silver and precious stones (1Corinthians 3:13-15). Therefore, it is by the spirit of judgment or the spirit of burning that the Lord purifies his people or “washes away their filth” (Isaiah 4:4).
The chaff seems to represent those who call themselves ‘Christian’ but are not real disciples of Christ. For whatever reason, they associate with Christians, perhaps even sitting among us during worship services, but they have never really submitted to Jesus as their Lord. They may have an idea of what the world should look like and work toward that end. Perhaps they perceive the Christian worldview as one that supports their ideal world and, therefore, identify themselves as Christian for the lack of a better name. In any event, if they haven’t submitted to Christ, they cannot be his disciples, because a disciple, by the very nature of the word, has submitted to and follows his leader. If this one is not one of Jesus’ disciples, he may call himself Christian, but he is not really Christian. He is separated from the good seed through the operation of the word of God. When the word brings persecution, he simply will not be able to endure.
The unquenchable fire seems to indicate the judgment of God, and some conclude it is the same fire as that mentioned in Luke 3:16, but others disagree. However, I believe the Scriptures show that the fires of the “spirit of judgment” are the same as the fires of the “spirit of burning” (Isaiah 4:4). Just as the great Cloud in the wilderness was light to Israel but darkness to the Egyptians (Exodus 14:20), so too the unquenchable fire is judgment to the ‘chaff’ (Mark 9:43-48) but a refiner’s fire to the good seed (Malachi 3:2-3), intended to bring forth good results (1Corinthains 3:13-15).
John indicated that Jesus would baptize with the Holy Spirit and fire (Luke 3:16), but it is a very serious matter to be brought into the presence of God, which the baptism of the Holy Spirit does. Such a baptism brings understanding of God’s word and empowerment to do his will. Therefore, those who are brought into his presence must be purified. Otherwise, we might end up like Nadab and Abihu (Leviticus 10:1-2) who came into God’s presence foolishly, according to their own desires and not the Lord’s.
 Thayer’s Greek Lexicon, en (G1722) means “in, with, by” etc.