Though the Epistle of Jude addresses much of the same content that the other epistles do, how the author does it is different. He quotes from the Book of Enoch and refers to Sodom and Gomorrah, the epic tale of destruction in the Old Testament. His use of this source material is not for the sake of drama, but rather to express the seriousness of what he relays in his letter. He wants his readers to grasp the dangers and consequences of false teaching. Though short, Jude is a significant epistle.
Authorship and Date

The author of Jude identifies himself as “the servant of Jesus and brother of James.” James, also known as James the Just, and Jude were the brothers of Jesus according to Matthew 13:55. Many have argued that the term brother could refer to half-brothers and often referred to cousins as well, either of which seems a more likely relation between Jude and Jesus. Jude is an alternative form of Judah and the Hebrew version of the Greek name Judas.
Whether a brother or cousin of Jesus, many scholars consider it unlikely that Jude would have the skills to write a letter on the literary level of the Epistle of Jude. They argue that the privilege of an education that included reading and writing was limited to the elites in Jewish society, which the extended family of Jesus did not seem to be. Jesus, however, could write according to John 8:6.

Because the Bible reveals little about Jude, the letter is exceptionally difficult to date. The errors it addresses were common in the first century CE and do not require a later dating like some other epistles do. It is like 2 Peter in content and could have been authored after it, which means it dates to 67-80 CE. Conversely, Jude could well have been authored before 2 Peter, which would imply a date of around 64 CE.
Several late 2nd-century Church Fathers accepted the authenticity of Jude, among them Clement of Alexandria, Tertullian, and Origen. However, Eusebius, a late 3rd and early fourth-century Church Father, had his doubts about the epistle’s author. It was nonetheless included in the Muratorian Canon in the 2nd century, accepted by Athanasius and the Council of Carthage in the 4th century, and included in the canon as we know it today.
Objections to Jude were based primarily on its use of noncanonical sources as material for its content. Jude 14-15 quotes the Book of Enoch (1 Enoch).
Historical Context

The letter by Jude provides no clue as to the intended audience. It could have been a Jewish, pagan, or mixed audience from anywhere in the Roman Empire since the issues it spoke to were widespread problems in early Christianity.
The reader can glean from the text that false teachers taught that the saving grace of God gave people license to sin and engage in immoral acts. Though fully-fledged Gnosticism is associated with the 2nd century and after, Jude may have been dealing with the thought that led to that belief system. Like several of the other general epistles, the author of Jude thought it imperative to warn believers against the false teachings some were spreading among 1st-century Christians.
The Epistle of Jude assumes knowledge of the Old Testament because it references many of the iconic figures and events from it. It mentions the Exodus, Satan’s rebellion, Sodom and Gomorrah, Moses’ death, Cain, Balaam, Korah, Enoch, and Adam.
Structure

Salutation (Jude 1-2)
Jude identifies himself and clarifies his relation to Jesus and James. He then identifies his audience in general terms as “those who are called” and kept by God and Jesus and extends a blessing.
Reason for the letter (Jude 3-4)
Jude notes that though he wished to write about salvation, he needed to address the false and perverted teachings that motivated his letter.
Warning against false teachers (Jude 5-16)
Jude starts his warning by calling to memory the judgment of the wicked in the past. He references unfaithful Israel, the fallen angels, and Sodom and Gomorrah. He then describes the apostates and their future judgment.
Exhortation to believers (Jude 17-23)
Jude calls on his readers to persevere and remain strong amid the challenges they face.
Doxology (Jude 24-25)
Jude gives praise and honor to God in his closing remarks.
Main Themes

Examples of the judgment of the wicked
Jude makes use of three instances where the wicked were judged. The first is the destruction of those in the nation of Israel who did not believe even after being saved from Egypt. Their disbelief resulted in a 40-year traverse of the desert during which all, except for a few that remained faithful like Joshua, passed away. The second is a reference to the impending destruction of the angels who Satan deceived to leave Heaven and follow him. Their destruction will be after the millennium, as described in Revelation 20. The third example is Sodom and Gomorrah, two towns destroyed due to their sexual immorality.
Warning against false teaching
Jude is one of only two epistles that mention an archangel in all scripture. He calls the archangel Michael, which correlates with Michael from Daniel 10 and 12, where the prophet refers to him as a prince. Paul, in 1 Thessalonians 4:16, says Jesus will come with the voice of an archangel. Though this verse speaks of the coming in a positive sense, 2 Thessalonians 2:8 shows the destruction of the wicked one (Antichrist) when Jesus comes.
Jude mentions Michael in the context of the slanderous utterances of the false teachers. He describes their character by comparing them to Cain, Balaam, and Korah, and shows that their words are empty and that they have no foundation. Jude quotes from the Book of Enoch to show how the destruction of these false teachers has been prophesied by Enoch even before the Flood.
Call to persevere
Jude calls on his readers to persevere and to remain merciful to others.
Key Passages

Jude 1:4
“For certain people have crept in unnoticed who long ago were designated for this condemnation, ungodly people, who pervert the grace of our God into sensuality and deny our only Master and Lord, Jesus Christ.”
From the words of the author, it is clear that the false teachers he warns about promote sexual immorality which is contrary to and denies the teaching of Christ to remain pure and holy.
Jude 1:14-15
“It was also about these that Enoch, the seventh from Adam, prophesied, saying, ‘Behold, the Lord comes with ten thousands of his holy ones, to execute judgment on all and to convict all the ungodly of all their deeds of ungodliness that they have committed in such an ungodly way, and of all the harsh things that ungodly sinners have spoken against him.’”
This passage from Jude has a strong correlation with 1 Enoch 1:9. Though not a verbatim quote, the correlation is clear. The use of an apocryphal book as a source caused some early Church Fathers to doubt the appropriateness of Jude as a book to include in the Biblical canon. Several Old Testament books, however, also refer to books not included in the Biblical canon.
Jude 1:17-18
“But you must remember, beloved, the predictions of the apostles of our Lord Jesus Christ. They said to you, ‘In the last time there will be scoffers, following their own ungodly passions.’”
Jude may be referencing the work of Peter or Paul here. Again, it is not a direct quote but relates the gist of 2 Peter 3:3, 1 Timothy 4:1, and 2 Timothy 3:1-5. If indeed Jude quoted from 2 Peter it follows that a later date for Jude must be accepted.
Contemporary Significance

Jude is relevant in contemporary society where Christianity faces challenges with changing views on sexuality and acceptable norms and standards. Unfortunately, how Jude is sometimes used may lead to accusations of hate speech and victimization.
Jude’s condemnation of immoral behavior is a call to godliness and to live according to the standards the Bible sets for believers. Just as early Christianity had significantly different norms to that of the ancient Greco-Roman world, Christianity has significantly different values to the secular worldview of modern times. The letter highlights the importance of community prayer and support for one another and to be vigilant, not accepting just any teaching, but considering it in the light of the teaching of the rest of scripture. The call to contend for the faith is as applicable today as it was when Jude wrote the work almost 2,000 years ago.