The vision on Patmos REV 1:9

John says he was there because of the word of God and the testimony of Jesus, language that points to exile for his Christian preaching rather than a voluntary stay. He describes himself as a brother sharing in the same tribulation as the churches he writes to, an old man among the last who had actually known Jesus. The island itself was a small, rocky place in the Aegean Sea, the kind of spot used to isolate troublesome people far from the mainland.

The phrase is generally understood as a reference to Sunday, the day Christians had come to associate with the resurrection, though the text itself does not spell that out. On that day John is suddenly in the Spirit and hears behind him a voice like a trumpet, loud and commanding enough that he turns to see its source. The moment marks the beginning of the vision, not just a note about the calendar.

What follows fills the entire last book of the Bible, so no short answer covers it fully, but it has two main movements. First come messages to seven actual churches of the time, each with its own situation and problems. Beyond those messages the vision stretches forward to a city coming down out of heaven where there is no more sea, an image of a renewed creation replacing the troubled present.

Christians read this differently, and the book itself resists a single simple label. The seven churches addressed were real communities with real, present problems, which has led many readers to see the book first as a message to its own time. Others emphasize the vision's reach toward a final city and a world with no more sea as evidence it is primarily about things still to come, and most readers hold both horizons together rather than choosing one.