Beloved, when I gave all diligence to write unto you of the common salvation, it was needful for me to write unto you, and exhort you that ye should earnestly contend for the faith which was once delivered unto the saints. (Jude 3)
I have addressed Jude 3 a few occasions on my blog, including Refuting Jeff Durbin on "Mormonism" and pp. 120-22 of my book, Not by Scripture Alone: A Latter-day Saint Refutation of Sola Scriptura. In a recent Catholic apologetics work, this verse was addressed in a rather cogent way, and similar to how LDS use it (I am not suggesting that the author holds to post-biblical revelation or a theory of "Great Apostasy" [he rejects both!] but that the idea that this verse supports Sola Scriptura and/or precludes doctrinal development is fallacious):
Catholics also believe [public revelation ceased at the death of the last apostle], but not on the basis of what Scripture alone says. For Protestants who derive their doctrines from Scripture alone, the closure of public revelation becomes a difficult doctrine to prove. Some have argued that this truth is described in Jude 3, which speaks of “the faith which was once for all delivered to the saints”, but this verse on its own cannot support the claim that public revelation has ceased. Many scholars think Jude was a source for Second Peter, which means Second Peter would not be a part of divine revelation, since it was written after the faith was “once for all delivered to the saints.”
Even if Jude were the last book of the Bible to be written, that wouldn’t prove public revelation ceased with the death of the last apostle. Protestant apologist John MacArthur says that the Greek word translated “delivered” in this verse refers to an act completed in the past with no continuing element”. He also says that the phrase “once for all” (Greek, hapax) means “nothing needs to be added to the faith that has been delivered ‘once for all’.” This would mean that the “faith” had been delivered before Jude was written, which means Jude and its teaching about the cessation of public revelation would not have been a part of the original Deposit of Faith. MacArthur even says this verse, “penned by Jude before the NT was complete, nevertheless looked forward to the completion of the entire canon.”
This shows that using Jude 3 to prove public revelation has ceased doesn’t work because it confuses “giving the faith” to the saints with public revelation. Jesus gave “the faith” once and for all to the apostles, but the public revelation of the faith continued for decades after his interactions with them during the writing of the New Testament. There isn’t any explicit biblical evidence that this revelation ceased after the death of the last apostle (or that it didn’t continue for centuries rather than decades). There is also no evidence that there were no more living apostles who would give such revelations. (Trent Horn, The Case for Catholicism: Answers to Classic and Contemporary Protestant Objections [San Francisco: Ignatius Press, 2017], 51-52, comment in square bracket added for clarification).
