Chapter twenty-one concludes St. John's account of Christ's earthly ministry. The chapter begins with an incident that is very similar to the way in which Jesus called some of the disciples (see Mark 1:16-20; Luke 5:1-11): He enabled the disciples to miraculously catch a large number of fish after a night spent without catching anything (21:1-14). St. John Chrysostom says that St. John recognized Jesus because he was more contemplative in nature, while St. Peter leaped into the water to race to Christ because he was more fervent and ready to throw himself into the situation before him.
Jesus is shown eating bread and fish to reinforce that He was risen, and was not simply a disembodied spirit. St. Cyril of Alexandria says about Christ's eating fish and honeycomb when He first appeared before the disciples (see Luke 24:36-43, expanding on the scene in John 20:19-20), "To produce in them a more firmly settled faith in His Resurrection, He asked for something to eat...He did this only to show them that the One risen from the dead was the same One Who ate and drank with them during the whole previous period of time when He talked with them as a man."
After breakfast, Jesus asked St. Peter three times if he loved Him—the disciple replied that he did—and then concluded by telling St. Peter to feed and tend His lambs and sheep (John 21: 15-17). There are two reasons for this exchange: St. Peter was the leader of the disciples, and therefore was first to profess his love for the risen Lord; and he previously denied Christ three times (18:15-27) and therefore needed to reaffirm His dedication to His Lord. St. Ephrem the Syrian explains it like this:
Jesus received the threefold (confession) that (Simon Peter) had professed as trustworthy pledges for the three (denials). Therefore, when his Master said (to him), 'Do you love Me?' our Lord was wanting to receive from him his true love so that, after having given the pledge of his love, (Simon) might receive (Jesus') sheep as a flock.
Jesus then prophesied St. Peter's death as an old man being led to his martyrdom (21:18-19); St. Peter was crucified upside down—because he did not believe himself worthy to be crucified in the same upright manner as Christ—during the reign of Nero in 67 AD. Some people believe St. Peter's subsequent question about St. John's future (21:21) demonstrates a jealousy that such a martyrdom was not prophesied for the younger disciple. St. John Chrysostom, however, replies that St. Peter asked the question out of love for St. John—St. Peter wanted to remain with his friend throughout any trials they might suffer, but Jesus simply responded that he should not be concerned with this, but only with his own obedience to Christ (21:22). The other disciples misunderstood Christ's words, "If I will that he remain till I come," to mean that St. John the Theologian would never die (21:23). In reality, however, the apostle reposed at approximately 100 years old sometime near the end of the first century.
The gospel account concludes with an affirmation that St. John (and probably his assistant, St. Prochorus of the Seventy) have written the truth, and at the same time reminding the reader and hearer that this account is far from exhaustive because no one book could record everything Jesus said and did (21:25; see also 20:30-31).