And the angels which kept not their first estate - A second case denoting that the wicked would be punished. Compare the notes, 2 Peter 2:4. The word rendered “estate” (ἀρχὴν archēn) is, in the margin, “principality.” The word properly means, “beginning, commencement;” and then that which surpasses others, which is “first,” etc., in point of rank and honor; or pre-eminence, priority, precedence, princedom. Here it refers to the rank and dignity which the angels had in heaven. That rank or pre-eminence they did not keep, but fell from it. On the word used here, compare Ephesians 1:2; Ephesians 3:10; Colossians 2:10, as applied to angels; 1 Corinthians 15:24; Ephesians 6:12; Colossians 2:15, as applied to demons.
But left their own habitation - To wit, according to the common interpretation, in heaven. The word rendered “habitation” (οἰκητήριον oikētērion) occurs nowhere else in the New Testament. It means here that heaven was their native abode or dwelling-place. They left it by sin; but the expression here would seem possibly to mean that they became “dissatisfied” with their abode, and voluntarily preferred to change it for another. If they did become thus dissatisfied, the cause is wholly unknown, and conjecture is useless. Some of the later Jews supposed that they relinquished heaven out of love for the daughters of men - “Robinson.”
He hath reserved in everlasting chains - See the notes, 2 Peter 2:4. Peter says, “chains of darkness;” that is, the darkness encompasses them “as” chains. Jude says that those chains are “everlasting,” (δεσμοῖς ἀΐ́δίοις desmois aidios. Compare Romans 1:20, “his eternal power and Godhead.” The word does not elsewhere occur. It is an appropriate word to denote that which is eternal; and no one can doubt that if a Greek wished to express that idea, this would be a proper word to use. The sense is, that that deep darkness always endures; there is no intermission; no light; it will exist forever. This passage in itself does not prove that the punishment of the rebel angels will be eternal, but merely that they are kept in a dark prison in which there is no light, and which is to exist for ever, with reference to the final trial. The punishment of the rebel angels after the judgment is represented as an everlasting fire, which has been prepared for them and their followers, Matthew 25:41.