Not all Jesus’ teachings were written down—the Bible says so. Jesus commanded “preach,” not “publish.”
The Church depended on oral preaching and written fragments and the Vetus Latina until the New Testament was completed through the work of St. Jerome in the 4th century A.D. St. Jerome was fluent in Aramaic, Hebrew, Greek, and Latin. He had—and was competent to translate—original documents that have been long lost to us and also had corroborating documents from the Early Fathers, only some of which we still have. He also had the Septuagint, because there was no complete Hebrew translation of the Old Testament. He meticulously winnowed wheat from chaff. His Latin Vulgate translation of both the Old and New Testaments was commonly used for a millennium before it was finally canonized as official by the Church at the Council of Trent.
Amusingly, there are people today who have neither the documents nor the linguistic fluency, but yet they think they can vet gnostic, Masoretic, hermetic, and other scriptural frauds.
Authentic Scripture is valuable; so is Apostolic Tradition. Read the Fathers who walked with Jesus and the Apostles. Believe the Bible and the traditions passed on by the preaching of the Apostles as the Bible commands.
Three questions for Protestants to ponder:
So, by the Protestant “Bible only” standard, the first three centuries of Christians were wrong because they obeyed oral tradition. Go figure.
The irony is this—the only bridge between Jesus Christ on Earth and the bowdlerized Protestant “Bible” today is… (angelic trumpets here)… oral tradition, the very same oral tradition that Protestants despise and ridicule.
Sola scriptura is self-contradictory (“Believe the Bible… except when it rejects Protestant theology”) and so invalidates Protestantism. Sola scriptura is completely inconsistent with the timeline: The only complete Scriptures at the time of Jesus and the Apostles were in the Septuagint. Jesus refers to the Old Testament in, for example, John 5:39. How could Jesus or the Apostles insist on believing only the Old Testament? ...or New Testament written sources that had not yet been put to paper? “Don’t believe anything we preach, except what is later going to be put down on paper.” A truly nutty doctrine.
The only rational interpretation is this: The Bible is valuable (2 Timothy 3:16), but not everything (John 21:25); Apostolic Tradition, the preaching “heard,” is essential (see the verses above) not only to determine what is canonical, but also because not everything Jesus said could be put down in a book. Sola scriptura is one of the most fundamental reasons that Protestantism fails: Without the oral traditions of the Apostles, Disciples, and Fathers of the first three centuries A.D., there would be no basis to judge what belongs in the canon of Scripture.
See also: The “Bible Alone” is Not Enough • Answers to 25 Questions on the History of New Testament that refute the Protestants’ “Bible Only” Theory.