Jude 1:7

7 likewise. Sodom, Gomorrah, and the other cities resemble the angels of v. 6 in the immorality and perversity of their sexual transgression. The comparison could also point to the flagrancy and pride with which they deserted their proper place.

an example . . . punishment of eternal fire. The fiery destruction of Sodom and Gomorrah and the surrounding towns in Gen. 19 serves throughout Scripture as a model of God’s judgment on sin (Deut. 29:23; Is. 1:9; Jer. 49:17, 18; Rom. 9:29).