Jesus says -
The Comforter, the Holy Spirit whom the Father will send in my name, He shall teach
you all things and will bring all things, to your remembrance, everything I have spoken to you.
The Holy Spirit brought all things to the disciples remembrance. Who is the source of the Gospels? It is the Holy Spirit. Jesus is addressing the apostles. Since the Holy Spirit brought Jesus' words to each apostles remembrance what need did they have to copy Jesus' words from each another? Do you think an editor would ever include such as statement? It would deny his work.
For no editor would think of drawing an important quotation: a climatic quotation from (Jn. 2:19), forming part of the plot, and put it in other books. (Matt 26:61 & Mk 14:58) He would quote from the same book. He would put the original statement and its quote in the same book, otherwise it takes away from the literary qualities. Without literary dependency there can not be an editor, because an editor takes a portion of one document and adds it to another document: i.e copying. The way dialogue is intertwined in the Gospels absolutely rules out literary dependency.
there are many other signs which Jesus did in the presence of His disciples, which are not written
in this book. (Jn. 20:30)
If, as some say, an editor, compiled this Gospel as much as 200 years after the event, how would he know that
Jesus did many other things, even it were only after 20 years. A collection of sayings could not include a saying
like that. But if a redactor did have other material,
a source, it would never be discarded, because that material
would have not only equal standing but greater standing as that recorded in the Gospels i.e as the word of God.
But no remains of a written source have ever been found.
We must consider the Jews to be faithful in their keeping of the Scripture, (Rom: 3:2) because Jesus condemned them for many things but not for a failure to keep the Scriptures intact. The Galileans, although somewhat despised, nevertheless were Jews and they would keep the same tradition of reverential care for the Scriptures.
IN THE BEGINNING WAS THE WORD...(Jn. 1:1)