St. John of Damascus:
The eyewitnesses and ministers of the word not only handed down the law of the Church in writings, but also in certain unwritten traditions. For whence do we know the holy place of the skull? Whence the memorial of life? Does not a child learn it from his father without anything being written down? It is written that the Lord was crucified in the place of the skull and buried in a tomb, that Joseph had hewn in a rock; but that these are the places now venerated we know from unwritten tradition, and there are many other examples like this. What is the origin of threefold baptism, that is with three immersions? Whence praying facing the East? Whence veneration of the cross? Are they not from unwritten tradition? Therefore the divine apostle says, So then, brethren, stand firm and hold to the traditions which you were taught by us, either by word of mouth or by our letter. Since many things have been handed down in unwritten form in the Church and preserved up to now, why do you split hairs over the images? Manichees composed the Gospel according to Thomas; are you now going to write the Gospel according to Leo? I do not accept any emperor who tyrannically snatches at the priesthood. Have emperors received the authority to bind and loose? ... I am not persuaded that the church should be constituted by imperial canons, but rather by patristic traditions, both written and unwritten. For just as the Gospel was proclaimed in all the world in written form, so in all the world it has been handed down in unwritten form that Christ the incarnate God should be depicted, and the saints, just as the cross is venerated and we stand to pray, facing the East.