John 21:19-23

Now He said this to indicate the kind of death by which Peter would glorify God. And after saying this, He said to him, “Follow Me [walk the same path of life that I have walked]!” Peter turned and saw the disciple whom Jesus loved following them; the one who also had leaned back on His chest at the supper and had said, “Lord, who is it that is going to betray You?” So when Peter saw him, he asked Jesus, “Lord, and what about this man [what is in his future]?” Jesus said to him, “If I want him to stay alive until I come [again], what is that to you? You follow Me!” So this word went out among the brothers that this disciple (John) was not going to die; yet Jesus did not say to him that he was not going to die, but only, “If I want him to stay alive until I come [again], what is that to you?”