Gregory the Great — as excerpted in the Catena Aurea on Luke 3:15-17

“(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.”