That there is not only solid evidence of oral tradition in the New Testament, but that Christians were commanded to hold to the oral tradition (along with the written tradition) is also based on solid evidence, and I will draw the immediate implications of these facts.
First, let's examine the evidence (all emphases below added).
We note the preaching of the Gospel has always been by oral peaching, even if literary forms of the Gospel are canonized in our Scriptures. So we are not surprised to hear St. Paul say to the Thessalonians:
Because of this we also give thanks to God unceasingly, so that when you received the word of God which you heard from us, you received not the word of men, but just as it truly is, the word of God, which also is at work in you who believe. (1 Thessalonians 2:13)
Indeed, the Apostolic transmission of this Gospel was essential to God's redemptive plan for the cosmos. The writer to the Hebrews exhorts his readers:
[H]ow shall we escape if we neglect so great a salvation, which in the beginning was spoken by the Lord, and was confirmed to us by those who heard Him (Hebrews 2:3)
St. John echoes this:
That which was from the beginning, which we have heard, which we have seen with our eyes, which we have gazed upon, and our hands have handled, concerning the Word of life--and the life was manifested, and we have seen, and bear witness, and we declare to you the eternal life which was with the Father and was manifested to us--that which we have seen and heard we declare to you, in order that you also may have fellowship with us; and indeed our fellowship is with the Father and with His Son Jesus Christ. And these things we write to you that our joy may be fulfilled. And this is the message which we have heard from Him and we announce to you, that God is light and in Him is no darkness at all. (1 John 1:1-5)
From the beginning of the world, God's redemption is communicated orally. Not only that, however, it is also transmitted from generation to generation orally. St. Paul writes:
The things which you learned and received and heard and saw in me, practice these things; and the God of peace shall be with you. (Philippians 4:9)
Note that St. Paul does not spell out in detail to the Church in Philippi all the things that they had “learned and received and heard and saw” in him here in his epistle to them. He presumes a certain content to their understanding, a content embodied by his way of life among them, that he need only note in summary here in his epistle. That is to say, there was an oral tradition in addition to his letter which he calls them to practice.
St. Paul goes on to say to St. Timothy:
Hold to the pattern of sound words which you have heard from me, in faith and love which are in Christ Jesus. (2 Timothy 1:13)
St. Paul doesn't say here, “Put into practice the Scriptures you have studied from your youth,” but enjoins upon them the things they hear and saw him say and do. Which is not to say that St. Paul would not want St. Timothy to put the Old Testament into practice; but it is to say that it was the oral tradition St. Timothy was to put into practice.
Note also that this exhortation, and the following one, are from the very same text that will later claim that all Scripture (the primary reference here is to the Old Testament) is “God-out-breathed,” and is profitable for the leaders of the Church in their ministry to Church members of teaching, reproof, correction and training in righteousness (3:16-17). Indeed, it is ironic that those who misinterpret these verses to teach the all-sufficiency of Scripture (over and against oral tradition), fail to reckon with the fact that St. Paul does not enjoin St. Timothy to “ask for the ancient paths of the Lord” (Jeremiah 6:16), but instead exhorts him to “hold to the pattern of sound words” which he had heard from St. Paul. He continues to exhort St. Timothy:
And the things which you have heard from me through many witnesses, commit these to faithful men who will be competent to teach others also. (2 Timothy 2:2)
Again: St. Timothy was not enjoined to write about it, nor to disseminate th