Peter turned and saw the disciple whom Jesus loved following them. He was the one who had leaned back against Jesus at the supper to ask, “Lord, who is going to betray You?”
20. And Peter, turning about. We have in Peter an instance of our curiosity, which is not only superfluous, but even hurtful, when we are drawn aside from our duty by looking at others; for it is almost natural to us to examine the way in which other people live, instead of examining our own, and to attempt to find in them idle excuses.
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
Then Peter turning about,.... After he was risen, and was following Christ: seeth the disciple whom Jesus loved following also; by whom is designed John the Evangelist, and writer of this Gospel; who hearing Christ bid Peter follow him, rose up likewise, and went after him, in token of his willingness to serve him, and suffer for him too: which also leaned on his breast...