Although we cannot pinpoint the exact dating of the book, or whether it was written before or after 2nd Peter, we can have assurance of the content which indicates the books purpose. This helps us to understand the audience to whom Jude may have written to. The fact that Jude wrote from a predominately Jewish background, and given his many allusions to the Old Testament apocalyptic literature, doesn’t allow us, however, to concretely identify the audience. What is does do is show us that Jude was quite familiar with the Old Testament. Some commentators have sought to take the Jewish content to clearly reveal the audience . Though Jude would certainly have intended his readers to have working knowledge of the Old Testament, it doesn’t necessitate a particular audience.
Now let’s take a look at how Jude used the Old Testament to illustrate the acts God’s judgment, paying special attention on how the poetic imagery and rhetorical patterns he used to develop his point even further.
Like many of the OT prophets Jude uses several events in the past to exemplify and argue his case . Jude chooses to voice the judgment of God on the men whose sole purpose is to destroy the grace of God. Though it may not have been so obvious a transgression, these men who pervert the Gospel are to be reckoned damned; indeed they we destined beforehand for such.
Lets look at two verses that illustrate this very idea . The first is verse 5. Here Jude makes reference to Jesus saving those out of Egypt  and then condemning those who did believe. This event in Jewish history was so tremendous and so poignant in depicting God’s redemptive acts for Israel that is basically had become synonymous with who God was upon identification . But the main thrust of Jude is the negative side of the act, namely the Lord condemning those who did not believe. This is clear from the context as Jude then continues to illustrate the place of the angels as they disobeyed and receive the judgment of God.
Another verse in which Jude used from the Old Testament in a severe fashion is verse 7, referring to Sodom and Gomorrah. The purpose of this reference was to show how God did not spare these cities in order to show his fierce wrath against ungodliness. The same outcome will be for the men of Jude’s day (and ours) who attempt to supplant the truth of God as proclaimed by Christ and his Apostles with something wholly other. He also uses this circumstance to show that it wasn’t just those who falsely teach strange doctrines, but rather those who forthrightly disobey in practice.
I now want to show how the poetic imagery and rhetorical patterns displayed in Jude were used to develop his point even further. What is unique about Jude is frequent use of imager in typical Hebraic poetic style. We find very limited amount of imagery used in the NT epistles. An example of this is in verse 12 and 13. There he states that unreasonable men are waterless clouds, swept along by winds; fruitless trees in late autumn, twice dead, uprooted; 13 wild waves of the sea, casting up the foam of their own shame; wandering stars, for whom the gloom of utter darkness has been reserved forever. It is clear that Jude intended to use the pictures from the creation to illustrate these men. A waterless cloud could be a reference to the very opposite of the NT idea of water. Throughout the Bible, ‘water’ or ‘living water’ is a metaphor for the Spirit. Rather than being springs of Living Water, or possessors of the Spirit of God, they devoid of the Spirit altogether.
Jude’s reference to fruitless trees is another NT comparison. Jesus spoke of being able to recognize a Christian by their fruit. The one who bears the fruit of eternal life will be manifestly obvious after a period of time. According to Matthew 12:33, Either make the tree good and its fruit good, or make the tree bad and its fruit bad, for the tree is known by its fruit. Jude couldn’t have made his point more clear with this reference. But notice that Jude states that they are fruitless. In the above statement Jesus says the all trees produce fruit, its just what kind of fruit they bear. Jude uses in rhetorical fashion the assumption that these people are actually born of God. The point made is that these men proclaim to be of Christ but are really not. The argumentation doesn’t surround the premise of non-Christians, for that is a concern rarely dealt with in the New Testament. Like Paul says, what right do I have to judge those outside the church ?
 MacArthur Study Bible. Intro to Jude.
 Indeed the book itself serves as an alarm to Christians and non-Christians alike
 It worth noting that Jude uses the Pentateuch with no direct reference to Moses. See New Dictionary of Biblical Theology, 355.
 This is a peculiar reference to Jesus as God. Though the some manuscripts generally use the word “kurios,” most translators agree that Jude more than likely had Jesus in mind because of the opening verses the book.
 Jehovah was the God who saved them out of Egypt to give them a land of their own. The repetition was to bring to memory the fact that even though the Jews were under such persecution from the Egyptians, God still had a plan to redeem them. Just as we see this phrase 9 times in Leviticus, 12 times in Deuteronomy, and numerous times throughout the Old Testament.
 1st Corinthians 5:12.