William Burkitt on Revelation 14:15

In the fifteenth verse we have a manifestation of the church's fervent desire that Christ would make speed, and hasten his work, and come quickly to judgment, both for the consummation of their glory, and for the destruction of his own and their enemies: Thrust in thy sickle, and reap, for the harvest is ripe; that is, it is full time to execute thy judgment on the wicked, for their sins (which call for these judgments) are now come to the height.

Behold here Christ's day of judgment is like a day of harvest; when the corn is ripe, the sickle is got ready; when the sickle is got ready, it is set to work; when it is set to work, it cuts down all, wheat and tares, corn and grass, without discrimination; but the Lord of the harvest soon commands a separation to be made of the good grain from the tares, of the righteous form the wicked, laying up the former in the granary of heaven, binding up the latter for the fire of hell.