Revelation 1:9. “I was on the island called Patmos.”
Zondervan‘s Pictorial Bible Dictionary says: “Patmos was the site of a penal colony, where political prisoners were condemned to hard labor in the mines.” (p. 721.) However, Leonard Thompson disagrees that Patmos was a penal colony at all:
The language of [Revelation] 1:9-10 does not give a hint of a suggestion that John was banished, deported, relegated, or imprisoned on Patmos; nor is there any evidence from Roman sources that Patmos was a prison settlement. Nor was it a deserted, barren isle, as is sometimes suggested; it had sufficient population to support a gymnasium two centuries before the Common Era, and around the time of John an inscription refers to the presence of the cult of Artemis.
Thompson’s grammatical analysis of this passage finds that John and his fellow Christians shared the life of Christ, not necessarily His persecution, and that they were suffering, with Christ, the necessary hardships in order to preach the Gospel on the isle of Patmos.