John 21:24-25
John Was an Eyewitness to Jesus
24 This is the disciple who testifies to these things and who wrote them down. We know that his testimony is true.
25 Jesus did many other things as well. If every one of them were written down, I suppose that even the whole world would not have room for the books that would be written.
John wrote much about Jesus in His Gospel According to John, and then in His three epistles...John was one of the Original Twelve Disciples...And he was the disciple who testified to these things in his gospel and who wrote them down, so we could believe...John knew that His testimony is true...And John tells us that Jesus did many other things as well...If every one of the things that He did were written down, then John supposed that even the whole world would not have room for the books that would be written...Jesus is that complex...
Jesus gave John the faith and the Light to believe...After Jesus resurrected John could see the Light and believed...