It is Paul who makes the
distinction of modes in which
the Revelation of God to His
People can be handed on.
Paul also called the process
of handing on the Word of
God "tradition."
He then terms two ways in which "traditions"
are transmitted, by word,
orally, and by letter, written.
2 Thessalonians 2:15
Therefore, brothers, stand firm and hold fast to the
traditions
(paradoseis)
that you were taught, either
by an oral statement or by a letter of ours.