Matthew Poole and continuators on Jude 1:7

7 Even as Sodom and Gomorrah, and the cities about them in like-manner giving themselves over to fornication, and going after strange flesh , are set forth as an example, suffering the vengeance of eternal fire.

Admah and Zeboim, Jer. 49.18. Hos. 11.8.

As Sodom and Gomoraah did, likeness of Sin inferring likeness of Punishment.

Margin, other Flesh, he means Male-flesh, which is other than what God appointed for that use they made of it; or, as we render it, strange Flesh, i. e. that which is strange, improper, and unfit for such an end. It is the Description of the unnatural Filthiness of the Sodomites, Gen. 19.5. See Rom. 1.26, 27.

Eternal Fire may be joined either, 1. with Example, and the words thus placed, are set forth for an Example of eternal Fire, suffering Vengeance; and the meaning is, That the Vengeance they suffered in being destroyed by Fire, is an Example, or Type of eternal Fire, that of Hell: Or, 2. with Vengeance, according to our Reading, and then the sense is, They are set forth for an Example, (viz. to those that after should live ungodly, 1 Pet. 2.6.) suffering the Vengeance of eternal Fire: The Vengeance they suffer, is an Example to deter others from the like Wickedness. This Fire is called eternal, either because of the still continuing Effects of it, or rather, because it was a Type or Representation of the Fire of Hell, and to those miserable Sodomites the very beginning of it, they being brought by these temporal Flames into everlasting Burnings.

Marginal references: Gen. 19.24. Deut. 29.23. 2 Pet. 2.6.; Gr. other.