Jude was the half-brother of Jesus. His brother James also the half-brother of Jesus and was the leader of the Jerusalem church in Acts 15 who also wrote the book of James. Jude 3 (ESV) Beloved, although I was very eager to write to you about our common salvation, I found it necessary to write appealing to you to contend for the faith that was once for all delivered to the saints. Jude had wanted to write on the general subject of our common salvation. But news reached him that his Christian friends were threatened by a dangerous heresy. Thus, he wrote a very different letter. This dangerous heresy made it necessary to alert believers to contend for the faith. The word, contend, only occurs only here in the NT. It literally means the intense effort in a wrestling match. Contend signifies “contend as a combatant.” The verb form shows that the Christian struggle is to be continuous. As used here “contend” means to emphasize that the defense of our faith will be continuous, costly, and agonizing. Jesus even warned us of these heretics.