Cain, Balaam, and Korah were the archetypal sinners of old. The heretics followed their pattern of behaviour and will therefore also endure their judgment. Jude mentions these individuals because he wants to dissuade the church, to whom he is writing, from following in their footsteps. He does this by reminding them of the final outcome of the heretics' way of life.1
11 Woe to them! For they walked in the way of Cain and abandoned themselves for the sake of gain to Balaam’s error and perished in Korah’s rebellion.