John 21:20 - Ellicott's Commentary On The Whole Bible

Peter, turning about, seeth the disciple whom Jesus loved following. — We must suppose that St. Peter had retired with our Lord, and that St. John seeing this had followed at a distance. He had been the companion and friend of St. Peter (comp. Introduction, p. 371). More than any other — and this is made prominent here — he had entered into close communion with the Lord Himself. He was called the “disciple whom Jesus loved” (comp. John 20:2, and Introduction, p. 375); he had leaned on His breast at supper, and, at a sign from Peter, had asked who was the traitor; he may well think that for him too there was some glimpse into the future, some declaration of what his path should be; or in that mingling of act and thought, of sign and thing signified, which run all through these verses, his following may indicate that he too, though he had never dared to say so, was ready to follow wherever the Master went.