In Jude we read of evil men crept in unawares, men who pollute the Church and corrupt its life and message. How do they do this?
Jude tells us they promote the 'way of Cain' who killed out of malice, pride, and a desire for standing before men and God. They also fall into the 'error of Balaam' who manipulated the word and corrupted the office of prophet. He hired out his services as he sought financial gain. And Jude also refers to the 'gainsaying of Core' who opposed Moses and sought to usurp his authority. His aspirations and actions served to subvert to the divine oracle.