And still another angel [the sixth] emerged from the altar and he had authority over the fire. And he called out with a loud voice to the one that had the sharp sickle, saying: ‘Put your sharp sickle in and gather the clusters of the vine of the earth, because its grapes have become ripe.’” (Revelation 14:17, 18)

The angel is commanded to begin his work by a message relayed through another angel that “emerged from the altar.” This fact is most significant, since faithful souls underneath the altar had asked: “Until when, Sovereign Lord holy and true, are you refraining from judging and avenging our blood upon those who dwell on the earth?” (Revelation 6:9, 10) With the harvesting of the vine of the earth, this cry for vengeance will be satisfied.