See on 2 Peter 2:6; cf. Gen. 19:23-28. Jude omits reference to Noah and the antediluvians and makes no mention of Lot (2 Peter 2:5, 7, 8).

 That is, the neighboring cities of Admah and Zeboim (Deut. 29:23), which Peter does not mention.

One word in Greek, used only here in the NT, and implying a complete abandonment to sexual debauchery.

 Or, “other flesh,” apparently a reference to the sin of sodomy as practiced by the inhabitants of the cities of the plain (see on Gen. 19:5).

 Gr. prokeimai, “to be placed before,” “to lie in sight.” The sin and fate of the cities of the plain have ever been held out as a warning of the terrible results that come from rejecting the righteous way of life. The unnatural Dead Sea, with its total absence of life and the strange qualities of its waters, serves to emphasize the nature of the wages paid by sin (cf. James 1:15).

The “eternal fire” that will eventually destroy all the ungodly is compared with the “eternal fire” that destroyed Sodom and Gomorrah. As the one was eternal in its effects, so will the other be.

Gr. hupechō, literally, “to hold under,” hence, “to undergo.” Jude’s use of the present tense implies that the destroyed cities are still undergoing their punishment. Their punishment is their state of utter destruction. Their punishment therefore continues.

Gr. dikē, “penalty,” “punishment.”

 See on Matt. 25:41. Some commentators have adopted the following interpretation of Jude’s words: “are set forth an example of eternal fire, suffering punishment”; but this rendering does not harmonize with 2 Peter 2:6, and is an unnecessary effort to avoid the problem connected with a correct understanding of “eternal fire.” The fire that annihilated the cities of Sodom and Gomorrah completed its work. When all that could be burned up had been burned up the fire went out. That fire has long since ceased to burn, but its effect will continue throughout eternity. It is in this sense that these cities suffered “the vengeance of eternal fire.”