9 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.
"This other author, on the contrary, did not even deem it sufficient to name himself once, and then to proceed with his narrative; but he takes up his name again, and says: "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."
The ecclesiastical writers have taught that at the time of Claudius Caesar, when that famine which the prophet Agabus had announced in the Acts of the Apostles would come in ten years time was at its height, that during that difficulty this same Caesar, impelled by his usual vanity, had instituted a persecution of the churches. It was during this time that he ordered John, the apostle of our Lord, Jesus Christ, to be transported into exile, and he was taken to the island of Patmos, and while there confirmed this writing. That he might present the trials of suffering which he was bearing at that time, he recalls that he was a participant in suffering, and then he adds the kingdom to the suffering of tribulation, and because of the kingdom to be received he further adds the patient endurance which he bore for the sake of Jesus.
I, John, etc. He hints at the person, place, time, and cause of the vision. He testifies that he saw it also in the Spirit, lest he be thought deluded by a fleshly apparition.
Was in the island, etc. The story is known, that John was banished to this island by Caesar Domitian because of the gospel, to whom it was fittingly given to penetrate the secrets of heaven when he was forbidden to exceed certain earthly spaces.
For the word of God, and for the testimony: is what he testified when he proclaimed the Gospel, he was exiled to Patmos. Eusebius told in his Canonical Chronicle in the time of Domitian.
[AD 532] Pseudo-Dionysius the Areopagite on Revelation 1:9