Jude gives three examples from the Old Testament - Cain, Balaam and Korah.
Cain's problem was jealousy. He was jealous of his younger brother on whose sacrifice God had sent a fire, accepting it. Are you jealous of a brother (perhaps younger than you) in whose life and ministry you see a fire and an anointing from God? Then you are following in Cain's footsteps. Whenever you are jealous of anyone, it proves that you don't love him. Elders can be jealous of younger brothers who are anointed and on fire and progressing spiritually beyond them. If you are jealous, you are in fellowship with the devil. A godly man will encourage such a younger brother. He will sit down in a meeting and let the younger brother be the main speaker.
Consider a father who is an uneducated labourer whose son goes to college and gets a degree. The father goes to the college to see his son getting his degree-certificate. Is he jealous of his son, because the latter has gone ahead of him educationally? No. Why? Because he is a father and he loves his son. If you as an elder in a church are jealous of anyone in your church, it is because you are not a father. A true father will encourage his son to go on and even get a Ph.D.! I have seen poor labourers who are happy to see their children well-educated. But it is rare to see an elder who is eager to push his younger brothers forward like that. Instead, I have seen elders who sit on their thrones and watch with a jealous eye some anointed younger brothers who they fear will be a threat to their authority - and they seek to suppress them in every way possible. The tragedy in Christendom today is that there are very few fathers. All seek their own. A truly godly man will be delighted to see young brothers maturing and having a greater anointing on their ministry than them. They will push such young brothers forward and withdraw into the background. If you want to be a godly elder be one like that - and not like jealous Cain.
The second example Jude quotes is Balaam. His problem was covetousness and the love of money. Balaam preached many good things - even about the coming of the Messiah (Num 24:17). But he also ran after money - exactly like many preachers today who preach wonderful truths and are just as covetous. Such preachers have gone the way of Balaam.
Thirdly, Jude speaks about Korah. His problem was rebellion against authority. Korah would have perished as a slave in Egypt. God never saw him fit to be the leader of Israel. He used Moses who delivered Korah from slavery. Moses encouraged him and even gave him a position of some leadership. But this went to Korah's head and he began to defy Moses. See how God judged him. The earth opened and swallowed him up. Cain was jealous of his younger brother. Korah was jealous of an older spiritual leader. You too can become proud and unsubmissive to godly men who led you and fed you - because you now think that you also are a spiritual leader. But God will vindicate those whom He has really anointed - and that day will be a sad day for you, as it was for Korah. Rebellion against authority is something that is unfortunately very common in Christendom. We should never rebel against spiritual authority anywhere. If you are not happy with a church, leave it and go somewhere else. But don't stay there and cause problems for the leadership. Otherwise you will end up like Korah. If you don't agree with a group, leave it and go elsewhere. Start another group if you like, but never cause rebellion anywhere. These men are hidden reefs - hidden rocks under the water's surface that ships crash on. They fool people into thinking that they have spiritual gifts - but they are like clouds that give no rain (Jude 1:12).