The Old Testament had repeatedly used the picture of a harvest to allude to God’s judgment coming upon the nations (Isaiah 21:10; Jeremiah 51:33; Hosea 6:11; Joel 3:13). In step with this pattern, Jesus too had spoken of a harvest at the end of the age (Matthew 13:30, Matthew 13:39; Mark 4:29; John 4:35). The vision John now sees forms the fulfillment of these prophecies of the final harvest.
15 And another angel came out of the temple, calling with a loud voice to him who sat on the cloud, “Put in your sickle, and reap, for the hour to reap has come, for the harvest of the earth is fully ripe.”