Of the doctrines and injunctions kept by the Church, some we have from written instruction, but some we have received from Apostolical tradition, by succession in private. Both the former and the latter have one and the same force for piety; and this will be contradicted by no one, who has ever so little knowledge in the ordinances of the Church. For were we to dare to reject unwritten customs, as if they had no great importance, we would insensibly mutilate the Gospel, even in the most essential points, or rather, for the teaching of the Apostles leave but an empty name. For instance: let us mention before all else the very first and commonest act of Christians, that they who trust in the name of our Lord Jesus Christ should sign themselves with the sign of the cross; who has taught this by writing? To turn to the east in prayer; what Scripture have we for this? The words of invocation in the change of the Eucharistic bread and of the Cup of blessing; by which of the saints have they been left us in writing? For we are not content with those words which the Apostle or the Gospel records, but both before them and after them we pronounce others also, which we hold to be of great force for the Sacrament, though we have received them from unwritten teaching. By what Scripture is it in like manner that we bless the water of baptism, the oil of unction, and the person himself who is baptized? Is it not by a silent and secret tradition? What more? The very practice itself of anointing with oil; what written word have we for it? Whence is the rule of trine immersion? and the rest of the ceremonies at Baptism, the renunciation of Satan and his angels? From what Scripture are they taken? Are they not all from this unpublished and private teaching, which our Fathers kept under a reserve inaccessible to curiosity and profane disquisition, having been taught as a first principle to guard by silence the sanctity of the mysteries?
St. Basil the Great