The Gospel of Saint John

John the Apostle, whom Jesus loved so much, was the brother of James the Apostle which was decapitated [beheaded] by Herod after the Passion of the Lord.
He wrote last of all the Gospels, having been asked by the bishops of Asia.
He wrote against Cerinthus and other heretics and especially against the doctrines of the Ebionites who claim Christ never existed before Mary.
That's why he was forced to expose the divine generation.
But there was also another reason that induced him to write.
Having read the books of Matthew, Mark and Luke, and having approved the records and testified that they had narrated true things, he observed that it was omitted to tell the story of one year from the imprisonment of John to the passion and death of Lord.

Leaving the year in which the stories were told by the three, he undertook to tell what had been done during the previous period, before John was put in prison, which is obvious to anyone who reads diligently the four Gospels, and it is particularly felt by those studies to eliminate any discrepancy between John and the other Evangelists.
... In the year 10, during the second persecution after Nero that was raised by Domitian, John was exiled to the Island of Patmos, where he wrote the Apocalypse, which was interpreted by Justin and Irenaeus.
Domitian was killed and during the reign of Nerva and by order of the Senate, the cruel acts were cancelled, and John returned to Ephesus, where he lived until the time of Emperor Trajan and where he founded and ruled all the Churches of Asia.
In the year 68 after the passion and death of Lord, he died and was buried in the same city.

• (St. Jerome: chapter IX of the book "De viris illustribus").