I rarely ever consult a commentary on any doctrinal issues, so what I believe is my personal understanding, and what my Holy Spirit has led me to believe, and because they may vary from others conclusions, that doesn't make either wrong, only different, and that is what makes the Holy Spirit so unique, that it is pure truth from God, but because it is a part of us it reasons using absolute truth, and what we give it to work with humanly, and it makes the best possible decisions based on that.
Is that scriptural? No, just what I have come to believe based on my knowledge and what the Holy Spirit adds to it.
1) Where did Jesus give instructions that the Christian faith should be based exclusively on a book?
1). Rev 1:11 What thou seest, write in a book,and send it unto the seven churches which are in Asia;
Rev 22:7 Behold, I come quickly: blessed is he that keepeth the sayings of the prophecy of this book.
10 And he saith unto me, Seal not the sayings of the prophecy of this book: for the time is at hand.
18 For I testify unto every man that heareth the words of the prophecy of this book, If any man shall add unto these things, God shall add unto him the plagues that are written in this book:
19 And if any man shall take away from the words of the book of this prophecy, God shall take away his part out of the book of life, and out of the holy city, and from the things which are written in this book.
Of course this deals directly with the book of Revelation, but God knew we weren’t going to have simply one book to represent the new Christian era, so since it deals with the end, it is simple logic that it would be the last book of what ever canon it was put in, and what ever canon God chose to survive is of equal authority.
The book of Revelations is written similar to the old Testament when God would tell his prophets to
Exo 17:14 And the Lord said unto Moses, Write this for a memorial in a book,
Rev 1:11 write in a book,and send it unto the seven churches
This was the same type of wordage used in Revelations so then we can conclude that this book is from God, then it is logical that what ever it references is also truth, and since it warns us of the things happening in the Gospels, such as the warning to the 7 Churches that are known Churches in the district of where the apostles taught and were developed by them into churches, then this gives them validity and connects them directly to God..
2) . 1 Cor 1:13 For we write none other things unto you, than what ye read or acknowledge; and I trust ye shall acknowledge even to the end;
The apostle Paul was approved by the same apostles that were taught by Christ, meaning he had the same authority as they, and since they all represented Christ, it was the same as Christ himself saying it.