John wrote the book of Revelation. He wrote of himself, “I John, who also am your brother, and companion in tribulation, and in the kingdom and patience of Jesus Christ, was in the isle that is called Patmos, for the word of God, and for the testimony of Jesus Christ” (Revelation 1:9).
We are told by a Roman historian of the day, Tertullian, that John was banished (presumably to Patmos) after miraculously surviving being plunged into boiling oil. The fifty-square-mile rocky island of Patmos (a visitors’ site today) had a Roman penal system at the time, where political criminals worked the mines.
John’s reason for being on the island was “for the word of God, and for the testimony of Jesus Christ,” so his work may have challenged Domitian’s empire, for Domitian had set himself up as a living god. John called himself a “companion in tribulation,” so it may have been during a period of persecution or harassment of Jews and Christians that he was officially exiled from setting foot in the Roman empire.
Sources:
http://en.wikipedia.org/wiki/John_the_Apostle
http://www.pilgrimtours.com/greece/info/patmos.htm
http://en.wikipedia.org/wiki/Domitian#Religious_policy
