Though it is possible that there was a previous correspondence from Jude,1 most likely he only wrote one letter to this church (the letter we have in the Bible). For this letter he was hoping to spend time marvelling and explaining the gospel, our common salvation.
2 This salvation consists of freedom (Jude 1:5), the gift of the Spirit (Jude 1:20), and the ability to live a pure life—all of which are offered freely because of Jesus’ death and resurrection. Instead of writing on these topics however, Jude was forced to write on a different topic, the matter of contending for the faith.
Somehow it came to Jude’s attention that there were individuals that had infiltrated the church and were teaching heresy (as is the case in 2 John 1:10). This situation has placed him under a strong obligation to act and call the church to action.
3 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.