Jude cited three examples of failure from the past to warn his readers of the danger involved in departing from God's truth. Divine judgment on flagrant evildoers is no novelty.29
Jude's introductory words were polite (cf. 2 Peter 1:12) but also a reminder that what he now said was fact beyond dispute. His readers knew these things "once for all"because God had delivered them "once for all"in Scripture (v. 3; cf. 1 John 2:20-21).
After God redeemed Israel and liberated the nation from bondage in Egypt, the people failed to continue to believe God's promises and to trust in His power (cf. Num. 14:11; Deut. 1:32). God judged those who failed by destroying them in the wilderness. He let that generation die rather than bringing the unbelieving apostates into the Promised Land. Some of the false teachers in Jude's day evidently were Christians. That is a reasonable conclusion since Jude compared them to the redeemed Israelites. They too were turning from continuing trust and obedience to God, and God would judge them as well.
"This allusion to Israel in the wilderness makes it very plain that Jude's opponents were once orthodox Christians who had gone wilfully [sic] astray into error."30
Other interpreters believe Jude was referring to those Israelites who had never really believed in Yahweh in this verse.31Jude primarily wanted to point out the behavior of these false teachers, not to identify whether they were believers or unbelievers. Unbelief always results in some kind of destruction whether the unbeliever is lost or saved. God definitely destroyed these unbelievers physically. He also destroyed them eternally if they were unsaved.
"Jude insists that the Saviour can also be the Destroyer."32
A group of angels also did not remain in their privileged position near God but left that sphere and so incurred God's wrath. Some interpreters believe Jude alluded here to Genesis 6:1-4 (but cf. Matt. 22:30).33Others believe he was referring to the rebellion of some angels that resulted in Satan's expulsion from heaven. The second explanation seems more probable to me. The apocryphal Book of 1 Enoch described this rebellion that Jude may or may not have had in mind here.34The rebellious angels he referred to are now in bondage and await God's judgment (cf. 2 Peter 2:4). These appear to be different fallen angels from Satan's agents who are at work in the world today, namely, the demons who have considerable freedom.
Jude's point in this illustration was that the apostates in his day had also abandoned a position of great privilege and blessing, namely, the opportunity to serve and glorify God. God would also judge them severely because of their departure. The angels who fell were not elect. Perhaps the apostates in view here were unsaved though God intended them, as well as the Israelites, to be a group for His own possession.
"If the highest beings known in creation were subject to judgment, how much more sinful men!"35
This example shows God's judgment on those who practice immorality and sexual perversion, which the false teachers of Jude's day evidently felt liberated to practice. The fire that burned up the cities of the plain was the instrument of God's punishment. That punishment will eternally burn against those who disregard God's will (Rev. 20:15). Here Jude seems to have had in view false teachers who were unsaved.
Each one of these illustrations highlights a particular aspect of the false teachers' error. It was a sin of rebellion by professing and perhaps genuine believers. It was a proud departure from a position of superior privilege. Moreover it involved immoral behavior, which the Gentile pagans practiced.
"No matter who may be the sinners, or what the circumstances of the sin, outrageous offences, such as impurity and rebellion, are certain of Divine chastisement."36
"When we examine these examples of the past, we discover that they are not chronologically arranged. . . . Why this unchronological arrangement in this Epistle? . . . We believe the arrangement is made in the manner as it is to teach us the starting point and the goal of apostasy. It starts with unbelief. . . . Unbelief leads to rebellion against God. . . . The predicted lawlessness with which this age ends is the fruitage of infidelity. Such is the development of apostasy. Unbelief, rebellion against God and his revealed truth, immorality and anarchy. These steps may be traced in our own times."37