Matthew 3:10

μὴ ποιοῦν, ‘if it bring not forth.’

ἐκκόπτεται, ‘is being cut down,’ the work has already begun. ἐκκόπτειν, used specially of cutting down trees. Cp. ἔκκοψον αὐτήν, Luke 13:7, and πίτυς μούνη πάντων δενδρέων ἐκκοπεῖσα βλαστὸν οὐδένα μετίει, Hdt. VI. 37. ἐκ denotes completion of act.

καρπὸν καλόν. The Oriental values trees only as productive of fruit, all others are cut down as cumberers of the ground. He lays his axe literally at the root. Land and Book, p. 341.