This letter is attributed to "Jude" (actually, Ioudas or "Judas" in Greek), the "slave/servant" of Jesus and "brother" of James (v. 1). But who is this?
The name was very popular among first-century Jews, since it is a variation of the name "Judah," one of the 12 sons of Jacob, patriarchs of the 12 tribes of Israel. Thus, there are several people named "Jude/Judas" in the NT; which one is meant here?
Certainly not "Judas Iscariot," since he was already dead (Matt 27:3-10; Acts 1:16-20; to avoid the negative associations, many NT translations call the others "Jude," rather than "Judas").
Probably not the "apostle" Jude/Judas, the son of James" (named in Luke 6:16 only), since Jude 17 refers to the "apostles of our Lord Jesus Christ" as a group distinct from himself.
Probably not the "prophet" Jude/Judas (also called Barsabas), who was sent with Silas from Jerusalem to Antioch (Acts 15:22-33).
The most likely candidate is the Jude who is named in the Gospels along with James and two others as the "brothers" of Jesus (Mark 6:3; Matt 13:55), since their families became prominent leaders of the early Christians in Palestine (Eusebius, EH 1.7.14; 3.19-20).
Many scholars have doubted that it was really written early and/or by someone so close to Jesus;
They propose that it was more likely written pseudepigraphically in the late first or early second century.
However, more recent studies suggest that the letter might well be authentic and early (from the 50's?).
The family and descendants of Jude were influential early Christians leaders, who would have wanted to preserve his letter.
The letter seems to rely on the Hebrew versions of the Jewish scriptures, rather than the Greek Septuagint quoted in the rest of the NT.
It presupposes strong familiarity with early Jewish apocalyptic traditions and the oral teachings of the apostles.
Nothing in the letter itself forces us to conclude that it must be late and pseudepigraphic.
Use of Scripture and Non-Biblical Texts:
The Letter of Jude never directly quotes from the Old Testament, but it alludes to several OT characters:
v. 5: the Israelites in the desert, who died in the wilderness due to their faithlessness (Num 14:1-35);
v. 6: the angels (or "sons of God"), who mated with mortal women (Gen 6:1-4; as interpreted by 1 Enoch 6-19);
v. 7: people of Sodom and Gomorrah, who sought to have sexual relations with the angels visiting Lot (Gen 19:4-11);
v. 11: Cain, who not only slew his brother Abel (Gen 4:1-16), but was the first "heretic," according to ancient Jewish traditions;
v. 11: Korah, who led a rebellion against Moses (Num 16:1-35).
It also quotes from some and alludes to some non-biblical ancient Jewish sources:
the apocryphal "1 Enoch" is alluded to in v. 6, and directly quoted in vv. 14-15;
the apocryphal "Assumption of Moses" is quoted in v. 9, and may have influenced the polemic of v. 16.
Finally, it quotes from some "predictions of the apostles of our Lord Jesus Christ," namely:
"In the last time there will be scoffers, indulging their own ungodly lusts" (vv. 17-18);
however, this quotation is not found anywhere in the canonical NT books;
instead, it must belong to other oral traditions that were not included in the NT.
The Letter of Jude makes its points not only by quoting from and alluding to popular ancient Jewish literature (both canonical and non-canonical), but it also uses several other interesting rhetorical techniques, including parallelisms and triadic (three-fold) illustrations:
Direct accusations against the "ungodly":
socially: they have infiltrated the community (v. 4a), but only seek their own benefit (v. 12), and divide the community (v. 19);
morally: they pervert the grace of God into licentiousness (v. 4c, 18), and do other immoral actions (vv. 8, 16a);
theologically: they "deny our only Master and Lord, Jesus Christ" (v. 4d); their speech is slanderous and bombastic (vv. 10, 16b).
Harshly polemical descriptions of the ungodly:
comparing them with evil people of the past (see "Use of Scripture" above)
describing them with metaphorical images: waterless clouds, fruitless trees, wild waves, wandering stars (vv. 12-13)
Direct appeals to the recipients of this letter:
"contend for the faith that was once for all entrusted to the saints" (v. 3)
"remember the predictions of the apostles" concerning the ungodly (v. 17)
"build yourselves up on your most holy faith..." (vv. 20-21)
"have mercy on some who are wavering, save others..., have mercy on still others" (vv. 22-23)
Encouragement, prayers and blessings for the recipients of the letter:
Recipients: "to those who are called, who are beloved in God the Father, and kept safe for Jesus Christ" (v. 1b);
Initial Blessing: "May mercy, peace, and love by yours in abundance" (v. 2);
Concluding Doxology: "Now to him who is able to keep you from falling, and to make you stand without blemish in the presence of his glory with rejoicing..." (v. 24).