A.T. Robertson Commentary Revelation 14:18

"And another angel came out from the altar, he that hath power over fire; and he called with a great voice to him that had the sharp sickle, saying, Send forth thy sharp sickle, and gather the clusters of the vine of the earth; for her grapes are fully ripe." — Revelation 14:18 (ASV)

Another angel (αλλος αγγελος). The fifth angel above Swete terms "the Angel of vengeance." He responds to the call of the sixth angel here as Christ does to the call of the fourth angel in verse 15.

Out from the altar (εκ του θυσιαστηριου). From the altar of incense where he is in charge of the fire (εξουσιαν επ του πυρος). If it is the altar of burnt offering (6:9; 11:1), we are reminded of the blood of the martyrs (Swete), but if the altar of incense (8:3,5; 9:13; 16:7), then of the prayers of the saints.

The sharp sickle (το δρεπανον το οξυ). Useful for vintage as for harvesting. So "send forth" (πεμψον) as in verse 15.

Gather (τρυγησον). First aorist active imperative of τρυγαω, old verb (from τρυγη dryness, ripeness), in N.T. only Re 15:18f. and Lu 6:44.

The clusters (τους βοτρυας). Old word βοτρυς, here only in N.T. (Genesis 40:10).

Her grapes (α σταφυλα αυτης). Old word again for grapes, bunch of grapes, in N.T. only here, Matthew 7:16; Luke 6:44.

Are fully ripe (ηκμασαν). Old and common verb (from ακμη, Matthew 15:16), to come to maturity, to reach its acme, here only in N.T.