Gregory the Great
Catena Aurea · Lukasevangelium 3
And as the people were in expectation, and all men mused in their hearts of John, whether he were the Christ, or not; John answered, saying unto them all, I indeed baptize you with water; but one mightier than I cometh, the latchet of whose shoes I am not worthy to unloose: he shall baptize you with the Holy Ghost and with fire. Whose fan is in his hand, and he will throughly purge his floor, and will gather the wheat into his garner; but the chaff he will burn with fire unquenchable.
(Mor. 15. sup. Job 20.) The fire of hell is here wonderfully expressed, for our earthly fire is kept up by heaping wood upon it, and cannot live unless supplied with fuel, but on the contrary the fire of hell,though a bodily fire, and burning bodily the wicked who are put into it, is not kept up by wood, but once made remains unquenchable.