Jamieson, Fausset and Brown on Mark 9:48

48. Where their worm dieth not, and the fire is not quenched--See on Mt 5:30; The "unquenchablesness" of this fire has already been brought before us (see on Mt 3:12); and the awfully vivid idea of an undying worm, everlastingly consuming an unconsumable body, is taken from the closing words of the evangelical prophet (Is 66:24), which seem to have furnished the later Jewish Church with its current phraseology on the subject of future punishment (see Lightfoot).