They said to you, "In the last times there will be scoffers who will follow their own ungodly desires." These are the men who divide you, who follow mere natural instincts and do not have the Spirit. (Jude 18-19)We are to be separate from those who divide. How do we recognize them? There will be other indications:
Warn a divisive person once, and then warn him a second time. After that, have nothing to do with him. You may be sure that such a man is warped and sinful; he is self-condemned. (Titus 3:10-11)
I urge you, brothers, to watch out for those who cause divisions and put obstacles in your way that are contrary to the teaching you have learned. Keep away from them. For such people are not serving our Lord Christ, but their own appetites. By smooth talk and flattery they deceive the minds of naive people. (Rom. 16:17-18)
I appeal to you, brothers, in the name of our Lord Jesus Christ, that all of you agree with one another so that there may be no divisions among you and that you may be perfectly united in mind and thought. (1 Cor. 1:10)
In the first place, I hear that when you come together as a church, there are divisions among you, and to some extent I believe it. No doubt there have to be differences among you to show which of you have God's approval. (1 Cor. 11:18-19)
They will secretly slip into the church (Jude 4).
After they are in, they will say that grace is freedom to sin (Jude 4).
They will deny Jesus Christ the Sovereign Lord (Jude 4).
They will gossip.
They will slander.
They do this so well that many of the believers fall for it and enter into their sins.