Luke 3:9

And even now the axe lieth at the root of the trees: every tree that bringeth not forth good fruit is hewn down, and cast into the fire.

Axe ... at the root ... This was a prophetic vision of the destruction of the Holy City which would ensue as a result of the rejection of Christ by Israel. The metaphor is that of a farmer who chops down an unfruitful tree and burns it. Too long Israel had been barren, as far as any fruits of righteousness were concerned; and her day of grace at the time John spoke was growing short.