ISB ~ Jude 1 v6

left their proper dwelling:Alludes to a Jewish tradition based on Gen 6:1-4 that rebel angels, called Watchers, came down from heaven to have sexual relations with women (1 Enoch 6-21; Jubilees 5, 1-11; Josephus, Antiquities 1, 73). Their wickedness brought swift punishment, as God imprisoned them in the dark chambers of the underworld to await their final doom. Jude reasons that if God punishes even angels, he will not hesitate to condemn godless men (CCC 391-95, 1033-39).