Early Church Fathers on Oral tradition
Whenever anyone came my way, who had been a follower of my seniors, I would ask for the accounts of our seniors: What did Andrew or Peter say? Or Phillip or Thomas or James or John or Matthew, or any of the Lord’s disciples? I also asked: What did Aristion and John the Presbyter, disciples of the Lord say. For, as I see it, it is not so much from books as from the living and permanent voice that I must draw profit (The Sayings of the Lord [between A.D. 115 and 140] as recorded by Eusebius, Ecclesiastical History, 3:39 [A.D. 325]).
For even creation reveals Him who formed it, and the very work made suggests Him who made it, and the world manifests Him who ordered it. The Universal [Catholic] Church, moreover, through the whole world, has received this tradition from the Apostles (Against Heresies 2:9 [A.D. 189]).
True knowledge is the doctrine of the Apostles, and the ancient constitution of the Church throughout all the world, and the distinctive manifestation of the body of Christ according to the successions of the bishops, by which they have handed down that Church which exists in every place, and has come even unto us, being guarded and preserved, without any forging of Scriptures, by a very complete system of doctrine, and neither addition nor curtailment [in truths which she believes]; and [it consists in] reading [the Word of God] without falsification, and a lawful and diligent exposition in harmony with the Scriptures, both without danger and without blasphemy… (ibid. 4:33 [A.D. 189]).
For wherever both the true Christian rule and faith shall be shown to be, there will be the true Scriptures, and the true expositions, of all the true Christian traditions (The Prescription of Heretics 19 [A.D. 200]).
Seeing there are many who think they hold the opinions of Christ, and yet some of these think differently from their predecessors, yet as the teaching of the Church, transmitted in orderly succession from the Apostles, and remaining in the churches to the present day, is still preserved, that alone is to be accepted as truth which differs in no respect from ecclesiastical and apostolic tradition (On First Principles Bk. 1 Preface 2 [circa A.D. 225]).
While [Ignatius of Antioch] was making the journey through Asia under the strictest military guard, he strengthened the diocese in each city where he stayed by spoken sermons and exhortations, and he especially exhorted them above all to be on their guard against the heresies which then for the first time were prevalent and he urged them to hold fast to the tradition of the Apostles to which he thought it necessary, for securities sake, to give form by written testimony (Ecclesiastical History, 3:36 [A.D. 325]).
Without prefixing Consulate, month, and day, [the Fathers] wrote concerning Easter, “It seemed good as follows,” for it did then seem good that there should be a general compliance; but about the faith they wrote not, “It seemed good” but, “Thus believes the Catholic Church”; and thereupon they confessed how they believed, in order to show that their own sentiments were not novel, but Apostolic; and what they wrote down was no discovery of theirs, but is the same as was taught by the Apostles (Letter on the Councils of Ariminum and Seleucia [A.D. 359]).
Of the beliefs and practices whether generally accepted or publicly enjoined which are preserved in the Church some we possess derived from written teaching; others we have received delivered to us “in mystery” by the tradition of the Apostles; and both of these in relation to true religion have the same force. And these no one will contradict; - no one, at all events, who is even moderately versed in the institutions of the Church. For were we to attempt to reject such customs as have no written authority, on the ground that the importance they possess is small, we should unintentionally injure the Gospel in these matters… (On the Holy Spirit 27 [A.D. 375]).
Don’t you know that the laying on of hands after baptism and then the invocation of the Holy Sirit is a custom of the Churches? Do you demand Scripture proof? You may find it in the Acts of the Apostles. And even if it did not rest on the authority of Scripture the consensus of the whole world in this respect would have the force of a command. For many other observances of the Churches, which are do to tradition, have acquired the authority of the written law (The Dialogue Against the Luciferians 8 [A.D. 382]).
“So then brethren, stand fast, and hold the traditions which you were taught, whether by word, or by epistle of ours” (2 Thessalonians 2:15). Hence it is manifest, that they did not deliver all things by epistle, but many things also unwritten, and in like manner both the one and the other are worthy of credit. Therefore let us think the tradition of the Church also worthy of credit. It is a tradition, seek no farther (Homilies on Second Thessalonians [circa A.D. 400]).