It is generally believed that the author of the letter of Jude was the younger brother of Jesus, whose original name Judas was later shortened to Jude (Mark 6:3). Jesus’ brothers at first did not accept him as the Son of God and the Davidic Messiah (John 7:5), but the resurrection must have caused them to change their minds. They were among the foundation members of the Jerusalem church (Acts 1:14; cf. 1 Cor 15:7).
Jude’s purpose in writing his letter was to oppose a kind of false teaching which denied that practical self-control was necessary for those who had become Christians. They claimed that when a person passed into a higher experience of spiritual life, the deeds of the body could no longer affect the purity of the soul. In fact, immoral behaviour could be a sign of spiritual maturity. Jude’s response to this was to warn his readers that those who taught and practised such immorality were perverting the gospel and bringing judgment upon themselves (v. 1-16). True Christians, besides learning more of Christian truth, kept themselves pure and developed practical godliness in their daily lives (v. 17-25). The content of Jude is similar to that of 2 Peter. Perhaps one writer borrowed from the other; or, more likely, both used a kind of argument that was common in opposing the false teaching. Such false teaching was widespread during the latter half of the first century, and seems to have been yet another early form of Gnosticism.