Those who are false teaching blackest darkness has been reserved forever.

Jude 1:5-13
Though you already know all this, I want to remind you that the Lord delivered his people out of Egypt, but later destroyed those who did not believe.
These men speak abusively against whatever they do not understand; and what thing they do understand by instinct, like unreasoning animals - these are the very things that destroy them.
They are clouds without rain, blown along by the wind; autumn trees, without fruit and uprooted - twice dead. They are wild waves of the sea, forming up their shame; wandering star, for whom blackest darkness has been reserved forever.
Jude reminds his readers of examples from Jewish history and tradition: those who fall away, or give themselves up to pride to lust will suffer God's judgment.
These men reject authority. But they are marked out for destruction - as Sodom and Gomorrah were for their sexual immorality and perversion; as Cain was for murdering the brother whose lie showed up his own; as Balaam was for betraying his position as a prophet; and as Korah was for his rebellion against  God-given authority. The examples are carefully chosen. These are the very things of which these teachers are guilty.
Why?
Because these men they did evil things like their forefather will be destroyed by the Lord. The judgment will come upon them. So Jude remind them. No matter they understood or not understand, do not boast and proud.
Realized who I am, then speak what I should say.
How?
Be careful to speak and teaching in Spiritual life, for authority of judgment is belong to the Lord!