Expositor's Bible Commentary Commentary Matthew 3:12

"whose fan is in his hand, and he will thoroughly cleanse his threshing-floor; and he will gather his wheat into the garner, but the chaff he will burn up with unquenchable fire." — Matthew 3:12 (ASV)

Messiah’s coming will separate grain from chaff. A winnowing fork tossed both into the air. The wind blew the chaff away; the heavier grain fell, to be gathered up from the ground, while the scattered chaff was swept up and burned. The “unquenchable fire” signifies eschatological judgment (cf. Isaiah 34:10; 66:24; Jeremiah 7:20), i.e, hell (cf. 5:29).