(Jesus said this to show how Peter would die to give glory to God.) Then Jesus said to Peter, "Follow me!"
Peter turned and saw that the follower Jesus loved was walking behind them. (This was the follower who had leaned against Jesus at the supper and had said, "Lord, who will turn against you?")
When Peter saw him behind them, he asked Jesus, "Lord, what about him?"
Jesus answered, "If I want him to live until I come back, that is not your business. You follow me."
So a story spread among the followers that this one would not die. But Jesus did not say he would not die. He only said, "If I want him to live until I come back, that is not your business."
That follower is the one who is telling these things and who has now written them down. We know that what he says is true.
There are many other things Jesus did. If every one of them were written down, I suppose the whole world would not be big enough for all the books that would be written.