The Apostle John, whom Jesus loved so much, was Zebedees son, and brother of that James the Apostle beheaded by Herod after Our Lords Passion. He wrote his Gospel last of all, at the request of the bishops of Asia, who were battling Cerinthus and other heretics, especially the Ebionites. These were beginning to teach that Christ had no existence previous to His existence in Mary. And so John felt compelled to assert clearly the divine origin of Christ.
In the fourteenth year of his rule, Domitian inaugurated the second persecution after Nero. John was banished to the island of Patmos, where he wrote the Apocalypse, a book on which Justin Marytr and Irenaeus later commented. In the reign of Nerva, after the death of Domitian and the abrogation of his decrees by the senate because of their excessive cruelty, John returned to Ephesus. There he stayed up to the time of Trajan, founding and guiding the various church-communities of Asia Minor. Spent by old age, he died and was buried at Ephesus in the sixty-eighth year after the Passion of Our Lord.
When the holy Evangelist John was living at Ephesus and was far advanced in years, his disciples would carry him into church. Being unable to give a lengthy sermon, at each gathering he was accustomed simply to repeat the words, Children, love one another. His disciples and the brethren who were present, upon hearing these same words repeatedly, became impatient and asked, Master, why do you always say the same thing? Johns reply was wholly in harmony with his heart: Because it is the Lords commandment; and if you did nothing more, it would suffice.
Taken from The Hours of the Divine Office in English and Latin, Vol. I: Advent to Passion Sunday (Collegeville, Minnesota: The Liturgical Press, 1963), pp. 1208-1210.