Why are Jude 4-16 and 2 Peter 2:1-18 so similar?
There are many parallel passages in Scripture, but these two are more than just parallel, they are almost the same, close enough anyway that this deserves a look. Over the centuries there have been many theories and discussions among scholars of various doctrinal views, and while I’m happy to let them speak for themselves, I guess I should toss my thoughts out for your consideration, and then let you decide for yourself what you think. If your ultimate conclusion is something like “Who cares? I’ll just study His Word and do my best to be like Jesus” then you are probably wiser than the scholars…
It would seem to me there are four reasonable possibilities for this similarity:
First this could just be a coincidence. Jude and Peter both wanted to address a similar problem and came up with almost the same discussion. Maybe God inspired them both to write the same thing… We should probably not assume that inspiration is quite the same thing as dictation, however. This really isn’t likely when you consider how close the two passages are.
Second. Jude and Peter could both have taken this material from a third document. Say for instance that Bob sent them both the same letter, and then each one re-wrote it and sent it to their friends. If something like that happened, Bob’s letter is nowhere to be found, and have you ever heard of Bob? (OK, I made that one up, but you get the idea) This scenario strikes me as pretty unlikely, especially since it would have made up nearly all of Jude’s letter.
Third. Jude could have read Peter’s letter and adapted 2:1-18 into his own letter; quite a few scholars like this one. However, it is unusual for one writer to adapt something from another writer and shorten a passage in the process; they usually expand on the original. Having some practical experience in this area myself, I can attest to the fact that unless the original is excessively wordy, that’s hard to do.
Fourth. Peter could have read Jude’s letter and expanded on it in his second letter to fit a slightly different situation. I’m not a betting man, but if I were, this would be my choice.
I flipped through a few respected commentaries on this topic before I banged out this post, commentaries from more than one doctrinal view, and I was amazed at how certain commentators will announce to their readers that such and such is an obvious fact as though they knew the answer for a fact; such confidence! The only problem with this is that they don’t know it for a fact; no one does. If you are a “regular” Christian, and by that I mean a “non-academic” Christian, as opposed to one with a wall full of degrees from seminaries, I have a valuable tip for you, ready?
Beware commentators, preachers and teachers who always “know” every answer and who cannot or will not admit that sometimes they are going with their best guess! The truth is that there are some little issues, such as this one, that we just don’t know for certain.
No extra charge for the tip, it’s your lucky day!
I’ll post another “Bonus” topic tomorrow.

Appreciate the tip and the underlying statement that God’s mind is bigger and better than ours. And being so definitive about things that completely clear and beyond question means we speak from arrogance. Love your take. Thanks.
Thank you very much!
I will posit a fifth possibility. These letters were copied and passed around to neighboring churches, and spread from there, then read before the assembly. It’s possible that Peter was in an assembly when the letter was read and the passage stuck with him. Churches today will read a passage of the OT or NT before asking a guest to address the assembly. I would assume the same happened then as well, just as Jesus spoke in the synagogue after a scriptural reading, then commented on what was read.
Very possible!