Luke 3:9

“And even now the axe also lies at the root of the trees. Every tree therefore that does not bring forth good fruit is hewn down, and cast into the fire.”

For his baptism is no protection against the axe of God. Rather they must recognise that God's axe is ready to start work, and that He is ready to start cutting at the root of all the trees which do not produce good fruit (compare Luke 13:7 and see Isaiah 10:33). And once He has cut them down He will cast them into the fire. Fire is a favourite description of judgment throughout Scripture. Its searing heat destroys until nothing is left.

Alternately the term for ‘axe' may indicate a wedge put in place at the base of the tree ready to be driven in so as to bring the tree crashing down.

‘Hewn down and cast into the fire.' Compare Jesus' words in Matthew 7:19. This whole picture is in Jesus' mind there. He had probably heard this message of John and demonstrates that He had approved of it.

It is noteworthy that this picture of judgment is central in the chiasmus which covers Luke 3:1 (see above). On one side of it come John's stern and vivid warnings, especially vivid to an agricultural people. On the other comes their response as their consciences are awakened.

Before, however, we think of him as a blood and thunder preacher we must remember firstly that the only aspect of his teaching that we have is what the Gospel writers have chosen to give us for their own purposes, and that secondly most of his teaching is paralleled by Jesus Who also says much more severe things. The reason that the writers especially bring out this side of his ministry is because they are seeking to bring home the fact of the emergency of the hour.