Jude 1:12

with every wind of false doctrine, like meteors in the air; are never at a point, always unsteady and unsettled, and ready to embrace every new and upstart notion:to whom the mist of darkness is reserved for ever; the nature of their punishment is expressed by "darkness", the blackest darkness, the mist of darkness, and which Jude calls blackness of darkness, the same with utter darkness; and which signifies a most forlorn and uncomfortable condition, and is a righteous judgment, and just retaliation upon them who studied to darken counsel by words without knowledge; and the certainty of their punishment is signified by its being "reserved", even as the happiness of the saints, and the safety and sureness of it are represented by an inheritance reserved in heaven: and as God has his treasures, magazines, and stores of grace and mercy, felicity and glory, for his people; so he has his wrath and vengeance reserved, laid up in store with him, and sealed up among his treasures, which he will surely bring forth in his own time: and the duration of this punishment is "for ever"; it is a worm that never dies, a fire that is never quenched, Isa 66:24 Mr 9:44; it is everlasting fire and burnings, the smoke of which ascends for ever and ever