So Peter turned around and saw the disciple Jesus loved following them. [That disciple] was the one who had leaned back against Jesus at the supper and asked, "Lord, who is the one that's going to betray You?"
John 21:20-22 In-Context
Very truly I tell you, when you were younger you dressed yourself and went where you wanted; but when you are old you will stretch out your hands, and someone else will dress you and lead you where you do not want to go.”
Jesus said this to indicate the kind of death by which Peter would glorify God. Then he said to him, “Follow me!”
Peter turned and saw that the disciple whom Jesus loved was following them. (This was the one who had leaned back against Jesus at the supper and had said, “Lord, who is going to betray you?”)
When Peter saw him, he asked, “Lord, what about him?”
Jesus answered, “If I want him to remain alive until I return, what is that to you? You must follow me.”
Because of this, the rumor spread among the believers that this disciple would not die. But Jesus did not say that he would not die; he only said, “If I want him to remain alive until I return, what is that to you?”
This is the disciple who testifies to these things and who wrote them down. We know that his testimony is true.