Albert Barnes on Matthew 3:10

The axe is laid unto the root of the trees. Laying the axe at the root of a tree is intended to denote that the tree is to be cut down. It was not merely to be trimmed, to be cut about the limbs, but the very tree itself was to be struck. That is, a searching, trying kind of preaching has been commenced. A kingdom of justice is to be set, up. Principles and conduct are to be investigated. No art, no dissimulations, are to be successful. Men are to be tried by their lives, not by birth, or profession. They who are not found to bear this test, are to be rejected. The very root shall feel the blow, and the fruitless tree shall fall. This is a beautiful and very striking figure of speech, and a very direct threatening of future wrath. John regarded them as making a fair and promising profession, as trees do in blossom. But he told them, also, that they should bear fruit as well as flowers. Their professions of repentance were not enough. They should show, by a holy life, that their profession was genuine.

(s) "hewn" Jn 15:6