Pseudo-Chrysostom — as excerpted in the Catena Aurea on Mark 9:43-50

“(Vict. Ant. e Cat. in Marc.) Then He introduces the witness of prophecy from the prophet Isaiah, saying, Where their worm dieth not, and the fire is not quenched. (Isa. 66:24) He says not this of a visible worm, but He calls conscience, a worm, gnawing the soul for not having done any good thing; for each of us shall be made his own accuser, by calling to mind what he has done in this mortal life, and so their worm remains for ever.”