It seems pretty standard for commentaries to be written on the combination of 2 Peter and Jude. Obviously they both share the subject matter of false teachers, but I assume there are reasons beyond this for including them together, likely involving source criticism. Do scholars think one borrowed from the other? From a common Q-like source? Why are these books usually written about together?
It is often believed that the author of the second book references the first book. This is based on both using otherwise rare words (such as "multiply" in Jude 2 being used in 1 Peter 1:2 and 2 Peter 1:2) and themes ("our common salvation" in Jude 3 and "a faith of the same kind as ours" in 2 Peter 1:2). Whether Jude quotes 2 Peter or 2 Peter uses content from Jude (Bauckham also lists out the possibilities of both drawing from a common source and having the same author. He holds neither position), is debated (see the Introduction to 2 Peter in Expositor's Bible Commentary, Ed. F.E.Gaebelein, Zondervan 1976-1992). Conservative scholars usually date Jude between 60 and 90.
Jude and 2 Peter are very similar (see especially "Relation to Second Peter), especially Jude and 2 Peter 2. Some argue that Jude was the source** based on style, brevity (the belief that the shorter work came first), and believing that 2 Peter is psuedopigraphical. However, Wallace answers those arguments and makes several arguments for Petrine Priority.
- Jude's grammar and style are stronger than Peter.
- 2 Peter speaks of the false teachers as yet to come while Jude presents them as recently infiltrating the church.
- Jude 3 speaks as if the age of the apostles has ended. If so, Peter would have to be dead and 2 Peter already written.
- Jude 17 gives 3 strong indications of who came first. (As this is key to Wallace's argument, he will be directly quoted.)
(a) Jude seems to be saying that his audience ought to recall what Peter (and Paul and his associates) had said to them regarding the rise of false prophets. Again, here it should be noticed that the verse is almost identical to 2 Pet 3:2, though Peter is speaking about what would come while Jude is saying that the prophecy was fulfilled.
(b) Again, as in v 3, v 17 seems to indicate that the age of the apostles was past.
(c) Finally, although Jude 17 and 2 Pet 3:2 are almost identical in wording, there are significant differences:
2 Peter 3:2—“you should remember the predictions of the holy prophets and the commandments of the Lord and Savior through your apostles” (RSV)
Jude 17—“Remember the predictions of the apostles of our Lord Jesus Christ” (RSV)
What shows very clearly the literary connection between these two texts is not only the general thought, but some key terms and expressions, for example:
mnhsqh'nai tw'n proeirhme'nwn rJhmavtwn (Peter);
mnhvsqhte tw'n rJhmavtwn tw'n proeirhmevnwn (Jude)
There are two major differences, however: (1) 2 Peter speaks of “your apostles” while Jude speaks of “the apostles”; (2) 2 Peter reminds his audience of what the prophets and apostles said while Jude merely mentions apostles. As we have argued in our discussion of 2 Peter, “your apostles” probably refers to Paul and his associates. Peter’s point was to show not only that Paul was a genuine spokesman for God, but also that his message was in line with the OT prophets. Jude, however, drops the mention of the prophets, and makes the apostles more absolute. If anything, this suggests that Jude was written later and depended on 2 Peter. (He might not have personalized the apostles because now such a group would include Peter and Peter was not, technically, one of “your apostles”). It is quite inexplicable for the author of 2 Peter, reading Jude, to add prophets and personalize the apostles, while it is perfectly clear why an author, after the age of the apostles had ended, spoke of them in more absolute terms and quietly dropped mention of prophets since that did not suit his purpose.37 In light of this parallel between the two epistles, it is rather surprising to read Bauckham’s comment that “there is no convincing case of allusion to a written Christian source [in Jude] … ”38
** e.g. Terrance Callan, "Use of the Letter of Jude by the Second Letter of Peter," in Biblica 85 (2004), pp. 42-64.
Burton L. Mack, in Who Wrote the New Testament, page 207, says the letters attributed to Peter and Jude have been described together as the catholic epistles (from katholikos, general), because they are addressed to Christians in general, not to a particular congregation.
Mack also says they can be discussed together (and with 1 Peter) as ‘Petrine’ epistles because 2 Peter incorporates almost all of Jude in its new rendition. The message of 2 Peter is not very different from that of Jude, although Mack says some stylistic features of 2 Peter temper Jude’s rough priggery and the mythology is not quite as offensive. Bart D. Ehrman agrees, saying in Forged, page 69, Scholars have long recognised that chapter 2 and the beginning of chapter 3 sound very much like the book of Jude, although there are not many extensive exact verbal repetitions, but they share many of the same ideas, thoughts and often words.