Peter turned and saw the disciple following whom Jesus loved. When Peter saw him, he said to Jesus, "Lord, what about him?" Jesus said to him, "What if I want him to remain until I come? What concern is it of yours? You follow me." So the word spread among the brothers that that disciple would not die. But Jesus had not told him that he would not die, just "What if I want him to remain until I come? What concern is it of yours?" It is this disciple who testifies to these things and has written them, and we know that his testimony is true. (Jn 21:20-25)
https://bible.usccb.org/bible/readings/052723.cfm
As the Easter Season comes to a close, Peter has been restored to ministry and questions Jesus about the Beloved Disciple. Apparently, the Beloved Disciple has died. (And if Lazarus is the Beloved, then for good reason folks would believe that he would not die—since the Lord had raised him from the dead!) The writer of this added chapter to the Fourth Gospel tells us that the Beloved Disciple testifies to these things and has written them. That would make the core of the Fourth Gospel older than anyone has ever imagined.