St. Basil the Great, The Holy Spirit 27, 66 (375 AD)
Of the dogmas and kerygmas preserved in the Church, some we possess
from written teaching and others we receive from the tradition of the
Apostles, handed on to us in mystery. In respect to piety both are of the
same force. No one will contradict any of these, no one, at any rate, who is
even moderately versed in matters ecclesiastical. Indeed, were we to try to
reject unwritten customs as having no great authority, we would
unwittingly injure the Gospel in its vitals.
St. Epiphanius of Salamis, Against all Heresies 61, 6 (377 AD)
It is not necessary that all the divine words have an allegorical meaning.
Consideration and perception is needed in order to know the meaning of the
argument of each. It is needful also to make use of Tradition; for not
everything can be gotten from Sacred Scripture. The Holy Apostles handed
down some things in the Scriptures, other things in Tradition.
St. John Chrysostom, Homily on 2 Thessalonians 4, 2 (c. 400 AD)
Therefore, brethren, stand fast and hold the traditions which you have
been taught, whether by word or by our letter. From this it is clear that
they did not hand down everything by letter, but there was much also that
was not written. Like that which was written, the unwritten too is worthy of
belief. So let us regard the tradition of the Church also as worthy of belief.
Is it a tradition? Seek no further.
St. Augustine of Hippo, Against the Letter of Mani 5, 6 (397 AD)
If you should find someone who does not yet believe in the Gospel, what
would you answer him when he says: I do not believe? Indeed, I would
not believe in the Gospel myself if the authority of the Catholic Church did
not influence me to do so.
St. Augustine of Hippo, Letter to Januarius 54, 1, 1 (c. 400 AD)