The gospels written by Mark and Luke have a place in the New Testament, although the authors were not apostles; yet the writings of the “many who took in hand to set forth in order a declaration of those things which are most surely believed among us”, to whom Luke refers (1:1), are not in the New Testament. What governed the inclusion of some and the exclusion of others?
The answer is to be found in the belief the Jews entertained that the “collection of the sacred books was defined under Divine guidance, and closed at the Divine command”. The proof is in the pages of the Bible.
John Carter, The Oracles of God, page 65.