Jude, a brother of James and a half-brother of Jesus (1:1; Matthew 13:55), is the author of this general epistle. As he began a letter about the "common salvation," he felt compelled to issue a warning against certain false teachers who, under cover, were attacking the nature and work of Christ. At the same time, they were turning the gospel of grace into a message that permitted lascivious conduct. Jude apparently follows up on Peter's similar warnings (cf. 2 Peter 2:3-3:4). The book offers both caution and encouragement to Christians.