Those harvested are the earth,
a term which stands for its inhabitants, that is, “every nation and tribe and language and people” (Revelation 14:6). These include the same earthly inhabitants over whom the dragon had given authority to the beast and who in turn worshipped the beast (Revelation 13:7, Revelation 13:16).
16 So he who sat on the cloud swung his sickle across the earth, and the earth was reaped.