St. John and The Seven Churches
Acts 8:1 And Saul approved of their killing him.
On that day a great persecution broke out against the church in Jerusalem, and all except the apostles were scattered throughout Judea and Samaria. However the apostles remained in Jerusalem.
But there is one more scenario which says St. John warned to flee Jerusalem when it was surrounded by Roman armies. It is mentioned in Luke 21:20-21
20 When you see Jerusalem being surrounded by armies, you will know that its desolation is near. 21 Then let those who are in Judea flee to the mountains, let those in the city get out, and let those in the country not enter the city.
One of the most important things about St. John is that he ministered for three decades to Christians in and around Ephesus, writing the Revelation, the Gospel and three Epistles.
St. John was the leader of the Asian Church and he was targeted by Roman authorities to exil him to Patmos.
9 I, John, your brother and companion in the suffering and kingdom and patient endurance that are ours in Jesus, was on the island of Patmos because of the word of God and the testimony of Jesus. 10 On the Lord’s Day I was in the Spirit, and I heard behind me a loud voice like a trumpet, 11 which said: “Write on a scroll what you see and send it to the seven churches: to Ephesus, Smyrna, Pergamum, Thyatira, Sardis, Philadelphia and Laodicea.”