Bede the Venerable — as excerpted in the Catena Aurea on Mark 9:43-50

“(ubi sup.) But because the Lord had three times made mention of the worm and the fire, that we might be able to avoid this torment, He subjoins, For every one shall be salted with fire. For the stink of worms always arises from the corruption of flesh and blood, and therefore fresh meat is seasoned with salt, that the moisture of the blood may be dried off, and so it may not breed worms. And if, indeed, that which is salted with salt, keeps off the putrefying worm, that which is salted with fire, that is, seasoned again with flames, on which salt is sprinkled, not only casts off worms, but also consumes the flesh itself. Flesh and blood therefore breed worms, that is, carnal pleasure, if unopposed by the seasoning of continence, produces everlasting punishment for the luxurious; the stink of which if any man would avoid, let him take care to chasten his body with the salt of continence, and his mind with the seasoning of wisdom, from the stain of error and vice. For salt means the sweetness of wisdom, and fire, the grace of the Holy Spirit. He says therefore, Every one shall be salted with fire, because all the elect ought to be purged by spiritual wisdom, from the corruption of carnal concupiscence. Or else, the fire is the fire of tribulation, by which the patience of the faithful is proved, that it may have its perfect work.”