When Peter saw him, he asked, “Lord, what about him?”
In these verses, we have, I. The conference Christ had with Peter concerning John, the beloved disciple, in which we have, 1. The eye Peter cast upon him (Joh 21:20): Peter, in obedience to his Master's orders, followed him, and turning about, pleased with the honours his Master now did him, he sees the disciple whom Jesus loved following likewise. Observe here, (1.) How John is described.
Commenting on John 21:20-25
Peter seeing him, saith to Jesus,.... Peter took a great deal of notice of John, and very likely understood, that he meant by his rising up and following Christ, to signify his readiness for service and suffering in the cause of Christ: and therefore says, Lord, and what shall this man do?
Verse 21. What shall this man do? This question probably means, "What death shall he die?" But it is impossible to ascertain certainly why Peter asked this question. John was a favourite disciple, and perhaps Peter suspected that he would have a happier lot, and not be put to death in this manner.