Some interpret the baptism of fire as referring to the day of Pentecost. Acts 2:2-3.
Some believe that the baptism with fire refers to the Holy Spirit’s office as the energizer of the believer’s service, and the purifier of evil within. 1 Thessalonians 5:19.
We should understand that Matthew’s record is a very abbreviated account of John’s ongoing ministry. Vast multitudes were pursuing John as he preached in ‘the wilderness of Judaea’ Matthew 3:1 / Matthew 3:5.
Some in the crowd were sincere; they confessed their sins and were immersed by John in the Jordan Matthew 3:6. Others, quite obviously, were caught up in the emotionalism of the occasion. Among these were Sadducees and Pharisees.
John characterised these Jews as ‘offspring of vipers,’ who would be advised to “flee from the wrath that is to come” Matthew 3:7.
This possibly has a more immediate reference to the destruction of Jerusalem, the reference to ‘even now the axe lies at the root of the trees’ Matthew 3:10 but then, more remotely, to the final day of human reckoning, Matthew 3:12.
In light of this, consider the following:
The promise, ‘he shall baptize you in the Holy Spirit,’ has reference to the apostles. The Saviour’s testimony in Acts 1 establishes this: ‘For John indeed baptized with water; but you shall be baptized in the Holy Spirit not many days hence’ Acts 1:5
It will hardly be denied that there is a connection between Acts 1:5 and Matthew 3:11. The promise was fulfilled on Pentecost when the apostles received an ‘overwhelming’ measure of the Spirit’s power. Acts 2:1 ff.
The immediate context would suggest that it is an allusion to the final fate of the wicked. Verse ten says that ‘every tree that brings not forth good fruit is hewn down, and cast into the fire.’
Then, at the conclusion of verse twelve, Jesus continues: ‘whose fan is in his hand, and he will thoroughly cleanse his threshing-floor; and he will gather his wheat into the barn, but the chaff he will burn up with unquenchable fire.’
Why should the ‘fire’ of verse eleven be viewed as something different from that referenced in verses ten and twelve, without some sort of compelling justification?