There are dozens of references to a “threshing floor” in the Bible, some literal and some symbolic. In biblical days there was no machinery, so after the harvest, the grain was separated from the straw and husks by beating it manually. First there had to be a flat surface that was smooth and hard, and this was known as the threshing floor. The process of threshing was performed generally by spreading the sheaves on the threshing floor and causing oxen and cattle to tread repeatedly over them, loosening the edible part of cereal grain (or other crop) from the scaly, inedible chaff that surrounds it (Deuteronomy 25:4; Isaiah 28:28). On occasion, flails or sticks were used for this purpose (Ruth 2:17; Isaiah 28:27). Then winnowing forks were used to throw the mixture into the air so the wind could blow away the chaff, leaving only the good grain on the floor.
Both the Old and New Testaments refer to the threshing floor as a symbol of judgment. Hosea prophesied that, because Israel has repeatedly turned from God to false idols, His judgment upon them would scatter them to the winds as the chaff from the threshing floor. “Therefore they will be like the morning mist, like the early dew that disappears, like chaff swirling from a threshing floor, like smoke escaping through a window” (Hosea 13:3). Jeremiah pronounces a similar fate on the Babylonians who persecuted Israel, likening their fate to the trampled sheaves on the threshing floor (Jeremiah 51:33).
John the Baptist uses the imagery of the threshing floor to describe the coming Messiah who would separate the true believers from the false. The true followers of Christ will be gathered into the kingdom of God just as grain is gathered into barns, while those who reject Christ will be burned up “with unquenchable fire,” just as the worthless chaff is burned (Matthew 3:12; Luke 3:17). The wicked are often described as chaff that the wind drives away (Psalm 1:4; Isaiah 17:13). Similar imagery of the good grain being separated from the worthless weeds appears in the parable of the wheat and the tares (Matthew 13:36–43).