Cain, the first heretic, corrupted Adam’s race in attempting to justify his lawlessness by denying God’s righteousness and justice.
Jewish literature during the Intertestamental period came to view Cain as the archetypal sinner: one who sinned, sinned with impunity, and taught others in sin. (See 1 John 3:11; 1 Clem. 4:7; Josephus, Ant. 1:52-66; Philo Det. 32, 78 and Post. 38-39.) The Targums also painted Cain as one who was a heretic in that he denied the righteousness of God, believing that one could find fault with God, and as one who denied that there would be any future judgment or accountability for his sins. So Cain is wicked not just because he sins and leads others in sin, but also because he doesn’t believe God will ever hold him to account for his sin.
So when the false teachers are said to “walk in the way of Cain,” this is probably an indication that they imitated these sins and the attitude that justified them. Jude’s statement may also hint that walking in Cain’s paths will lead to Cain’s destruction.
Balaam corrupted Israel on account of his greed by leading Israel into idolatry through his prophecy which was for financial gain.
The reference to Balaam is a reference to greed. An account of Balaam is given in Numbers 22-24 and this reference is the only place, in or out of the Bible, where Balaam is cast in a positive light at all. In this text, Balaam is hired by Balak to curse Israel but instead, as a result of an incident involving an angel and his donkey, who speaks to him, is compelled to prophesy in favor of Israel.
Jewish tradition preserved commentaries on this account that portrayed Balaam as a prophet-for-hire who prophesies for the highest bidder out of greed. He is also portrayed as one who led Israel into debauchery and sin for the same fee. This tradition is preserved in Rev. 2:14 which says that Balaam “…taught Balak to put a stumbling block before the children of Israel, to eat things sacrificed to idols, and to commit sexual immorality.” (Note that Jude does not mention the idolatry.)
Several elements characteristic of the false teachers are evident in the reference to the Balaam tradition: false prophets, sexual immorality, leading others astray through false teaching, greed that motivates the false teaching, and the use of dreams to justify the teaching. Jude’s use of the verb “plunge” may signify (per Baukham, 82) that they follow in Balaam’s path eagerly but are in reality plunging headlong into Balaam’s destruction.
Korah led his followers to destruction in causing division in the people of God by disputing God’s law.
The final illustration of v. 11 is that of Korah. The story of Korah is found in Numbers 16:1-35 and 26:9-10 and is referenced again in Psalm 106:16-18 (cf. also Sirach 4:18-19). Korah was the archetypal lawless heretic in Jewish theology. Jude references Korah here to demonstrate the false teachers’ rebelliousness and the controversy they stir up which will eventually lead to judgment. Just as with the previous examples in this section, the judgment of Korah is also in view. Korah’s judgment, swallowed by the earth, was striking, visible, and unmistakable, as will be the judgment of the false teachers when they, too, perish.