Jude is a short letter s written by Jude, the half-brother of James, and it is addressed to all believers. The main theme of the letter is to encourage Christians to stay true to their faith and avoid false teachings and immoral behaviors. Jude argues that false teachers have infiltrated the church and are leading people astray, so he urges the readers to contend for the faith and stay focused on God's word. In addition, Jude warns about the judgment that will come upon these false teachers and encourages believers to build one another up in the faith.