Jesus repeatedly taught things that were not in the Scriptures. Read the Sermon on the Mount. He says more than once: “You have seen it written...But I say to you...” His teaching on marriage, his teaching on anger, his teaching on anger—in all those cases and more he taught something different from the Jewish Scriptures.
He taught “with authority,” rather than merely repeating what had been written.
And...every word and action of Jesus that we know about was communicated for decades by oral tradition before it was written down.
Different than Jewish scriptures? Not at all. He taught what was in the Word previously, as He was Himself the Word, although much of what He revealed had been previously hidden in plain sight as it were, but the sense of it still there, albeit best discernible by way of Spirit.
What He was doing was correcting the misconceptions and misapplications of the law, whenever He would say in a corrective/adjusting manner, "But I say to you". Fair enough?
That what He spoke differed in ways from what was more widely taught concerning scripture, does not mean He was introducing new principles, as much as He was expounding upon and illuminating the deeper, and thus true and actual meanings of what had already been carefully and deliberately, painstakingly revealed, over the course of many centuries, piece by piece, line upon line, precept upon precept, to Abraham, Moses & the prophets.
10 For precept must be upon precept, precept upon precept; line upon line, line upon line; here a little, and there a little:11 For with stammering lips and another tongue will he speak to this people.
12 To whom he said, This is the rest wherewith ye may cause the weary to rest; and this is the refreshing: yet they would not hear.
13 But the word of the Lord was unto them precept upon precept, precept upon precept; line upon line, line upon line; here a little, and there a little; that they might go, and fall backward, and be broken, and snared, and taken.
Had God been, up until the time He was born into this realm in the form of a man, holding out on the Jews, short-changing them, failing to provide to them that which they should pay heed to -- or was it more like it was all "there" already, but veiled from sight & conceptual grasp of "flesh"? I say to you and all, that it is still much hidden in that manner, much as Simon was told, "blessed are you, Simon Bar-Jonah, for flesh and blood did not reveal it to thee...".
Even when He did speak, teaching the nature of His Father's kingdom, He spoke in parables, which few at the time could understand.
As I already made note of, when He rebuked such as the Pharisees and Sadducees, and also when speaking to elders of Israel who knew the scriptures, He used the scriptures, and regardless what you say-- upon many occasions He didrepeat the scripture if not word-for-word, then closely enough, but more importantly -- perfectly, as to truth and meaning, which had been there previously, all along. Rebuking Satan himself, He spoke not by and with his own authority, but that of His Father, as it is written.
Decades? Barely...
But what are you driving at, what are you hinting at, precisely? Is there something important missing? Just WHAT is it, that was only transmitted "orally", that did not make it into either NT scripture itself, or that can be discerned by some careful study of the earliest NT church.
Should I accept things arising only centuries later, first peeking out a bit with some slight mentions, but then inflating over centuries time; to be this long lost "oral tradition" Romanist apologists are always hinting around about, when push comes to shove in RC efforts to smash "sola scriptura" as ultimate authority (touchstone for doctrine, if you will) and replace it with their own singular [and specious] claim to sola ecclesia?
Nice try, but I've seen that movie before.