2John 1
9Whosoever transgresseth, and abideth not in the doctrine of Christ, hath not God. He that abideth in the doctrine of Christ, he hath both the Father and the Son.
10If there come any unto you, and bring not this doctrine, receive him not into your house, neither bid him God speed: 11For he that biddeth him God speed is partaker of his evil deeds.
We have four Gospels which teach the doctrine of Christ, what more do we need?
And how did they get those Gospel stories? From person to person communication, right? The Gospels were written from roughly 50 AD through 100 AD.
Christ had ascended into heaven. So with the help of eye-witnesses and the Holy Spirit these Gospels were scribed.