Luke 3:15-18 meaning

The parallel gospel accounts for this passage are Matthew 3:11-12, Mark 1:7-8 and John 1:19-20, 26-27.

Something inspired and motivated all the people of Judea to trek into the wilderness to hear what John was saying. Luke tells us what this motivation was:

Now while the people were in a state of expectation and all were wondering in their hearts about John, as to whether he was the Christ (v 15).

The Jewish nation, under Roman oppression, was looking for their Messiah. What inspired and motivated all the people of Judea and Jerusalem to hear John's message? They wanted to know if he was the Messiah, the One who would fulfill their hopes and dreams (Matthew 11:7-9).

John understood the reason they came to him.

John turns the subject briefly to himself and the nature of his baptism as a segue to talk about the Messiah and His baptism. As for me, John says, I baptize you with water. John's baptism was meaningful but symbolic. It was administered by water and was a public display of a changed heart and mind. John's baptism indicated that the people he baptized wished to be prepared for the coming of Heaven's kingdom (Matthew 3:2). John could preach the message of repentance and immerse the penitent in water as a sign of their commitment to God and His approaching kingdom. But John explains that this is the limit of his ministry.

John also understood his role as the Messianic messenger (Mark 1:2). He addressed the people's expectations by saying: but One is coming who is mightier than I, and I am not fit to untie the thong of His sandals. The One who is coming who is mightier than I is John's expression for the Messiah. John made it absolutely clear that he is not the Messiah (John 1:19-20).

The word translated mighty is the Greek term, ἰσχυρός (G2478 - pronounced: "His-chu-ros"). It can mean "forcible, strong, valiant, or violent." John is saying that the One who is coming after me has more power and authority than I do. The use of "His-chu-ros" could additionally suggest that the Messiah will be far less gentle and mild than John is (i.e. He is more "violent/forceful" than I).

John then demonstrates the great gap between his worthiness and valor and that of the Messiah: I am not fit to untie the thong of His sandals. According to Jewish custom, removing someone's sandals was a task for the lowest servant of the house. John is saying that compared to the Messiah, he is unworthy to perform even this lowly task for the Messiah. Given the extent to which John was revered, this was quite a statement.

Having demonstrated his weakness and lowliness alongside the Messiah's power and glory, John then describes the nature of the Messiah's baptism. He will baptize you with the Holy Spirit and fire. John only immersed people in water, in a symbolic ceremony. The Messiah's elements for immersion are the Holy Spirit and fire. Fire is hot and intense. It burns. Fire purifies by consuming all impurities.

Fire is a frequently mentioned throughout the Bible as a symbol of God's presence. See God's covenant with Abram (Genesis 15:17); the Burning Bush (Exodus 2:2-5); the Pillar of Fire by night (Exodus 13:21); Isaiah before the throne of God (Isaiah 6:4); God is a wall of fire (Zechariah 2:5); the Spirit at Pentecost (Acts 2:1-4); God is a consuming fire (Deuteronomy 4:24; Hebrews 12:29).

Fire is a frequent symbol of God's judgment, both as a means of His wrath and as a means of sanctification. See Sodom and Gomorrah (Genesis 19:24); the Eighth Plague (Exodus 9:23); the Battle of Jericho (Joshua 6:24); Elijah and the prophets of Baal (1 Kings18:20-40); Isaiah in the presence of God (Isaiah 6:1-7); Warnings of the minor prophets (Zephaniah 3:8); Christ's Accounts of Gehenna and the Outer Darkness (Matthew 13:40, 42, 50; Mark 9:43-49); the Judgement Seat of Christ (1 Corinthians 3:11-15); God's wrath toward the degenerate (Hebrews 10:26-27); the Lake of Fire (Revelation 20:14-15).

These two common symbolic usages of fire demonstrating God's presence and judgement need not be exclusive. Both can be applied at the same time.

The Messiah's baptism is an immersion into God's presence that burns away all sin and impurity. It is at once painfully intense and wonderfully good. All who enter His kingdom will undergo the Messiah's baptism. John's message of repentance and call for baptism was a preparation. A way to lessen the future pain of burning refinement and prepare for the goodness of the Messiah's baptism.

John then gives another agricultural metaphor, this time describing the Messiah's baptism:

His winnowing fork is in His hand to thoroughly clear His threshing floor, and to gather the wheat into His barn; but He will burn up the chaff with unquenchable fire (v 17).

It bears a remarkable similarity to Paul's metaphor of Christ's evaluation of believers and their works in the Day of Judgement:

"For no man can lay a foundation other than the one which is laid, which is Jesus Christ. Now if any man builds on the foundation with gold, silver, precious stones, wood, hay, straw, each man's work will become evident; for the day will show it because it is to be revealed with fire, and the fire itself will test the quality of each man's work. If any man's work which he has built on it remains, he will receive a reward. If any man's work is burned up, he will suffer loss; but he himself will be saved, yet so as through fire."
(1 Corinthians 3:11-15)

John describes the Messiah as a reaper about to reap. His (the Messiah's) winnowing fork is in His hand, and He will thoroughly clear His threshing floor. The threshing floor is a hard surface where all the cut stalks from the grain harvest are laid to be beaten (threshed), so that the grains (the useful parts also called the wheat) become separated from their stalks (the worthless parts also called the chaff). John's reference is that the Messiah will harvest all the stalks (everyone) in his field (all of His people) and thresh the grains (the good works) from them at His threshing floor (place of judgment).

That the Messiah will thoroughly clear His threshing floor indicates that He will not lose a single grain. He will not forget a single good work. After He has done this, the Messiah will gather His wheat (the productive, edible grains) into the barn, but He will burn up the chaff (the part that isn't useful) with unquenchable fire. All the chaff, the inedible leftover stalks and husks, will be burned by Him with an unquenchable fire. This term suggests that these worthless parts will be completely burned up. They will not last or be remembered.

So with many other exhortations he preached the gospel to the people (v 18).

After relating John's statements about the coming Messiah and impending judgement, Luke summarizes the rest of John's teachings in the wilderness. To exhort means to "call near, invite, beg, entreat, beseech." An exhortation is a call to action. John was calling on the people with many exhortations to listen as he preached the gospel and to act upon its good news. The phrase translated preach the gospel is the Greek term, εὐαγγελίζω (G2097 - pronounced: "Yoo-ang-ghel-id'-zo"). It is a compound word consisting of "εὐ"/"eu" meaning "well done" or "good," and ἄγγελος/"ang-ghel-os" meaning "angel" or "messenger." In the New Testament it is used to describe the message of good news of the coming of God's kingdom and the salvation to be obtained through the Messiah Jesus. In keeping with his message from the previous verses, John was preaching to the people about the coming Messiah and His kingdom.