John Gill Commentary Luke 3:9

"And even now the axe also lieth at the root of the trees: every tree therefore that bringeth not forth good fruit is hewn down, and cast into the fire." — Luke 3:9 (ASV)

And now also the axe is laid unto the root of the trees ,
&c.] Not only to Jesse's family, which as a root in a dry ground, and to Jerusalem, the metropolis of the nation; but to the root of the vain boasting of every Jew; their descent from Abraham, the covenant made with him, their ecclesiastical state and civil polity, all which would quickly be at an end: the Romans were now among them, the axe in God's hand; by means of whom, utter ruin and destruction would be brought upon their nation, city, and temple:

every tree therefore which bringeth not forth good fruit is hewn
down, and cast into the fire;
(See Gill on Matthew 3:10).