Verses 14-16 again describe the rapture as first described in Revelation 7:13-14 but this time from a different perspective. Also, note the mention of the cloud. Every time Jesus second coming is written about, clouds are mentioned. In other places it's further described as the sun and moon being darkened and the stars not giving their light. The reaping goes back to the parable that Jesus gives in Matthew 13 where he explains that the harvest is at the end of the world. In it, there were good seed and tares. The good seed was harvested into the barn and the tares were gathered together and burned.