When is the tribulation to take place? Were the churches that John was writing to undergoing persecution, suffering, and tribulation as well?
B. Hodge, Biblical Authority Ministries, May 25, 2020
Many places in Revelation indicate the churches were already undergoing tribulation and suffering: Revelation 2:9-10; 3:9-10; 6:9-11; 11:7-18; 12:10; 13:10; 14:11-13; 16:5-6; 17:6; 18:20-24; 19:2; 20:4-6.
According to John, he is living in the tribulation as of the writing of the book of Revelation (Revelation 1:9). Furthermore, Jesus previously told the disciples in Matthew 24:9 that they will be delivered “up to tribulation and kill you, and you will be hated by all nations for My name’s sake.”
And so this confirms that the apostles, such as John, will be in it. John was banished to Patmos (where he wrote Revelation) for Christ’s name’s sake (Revelation 1:9). Peter and Paul were killed by the Roman emperor, Nero, per early Christian historian Eusebius (II.25).
Mark 13:19-24 also confirms that disciples will be in the tribulation. Even Paul informed those at Thessalonica that the tribulation would come and had forewarned them. He writes to them while they were undergoing it (1 Thessalonians 3:1-6). So this should call into question the interpretation that the recipients of the letter of Revelation would have had in mind a tribulation in the far future.
Read Revelation 10:11-18:24. (Yes again, this seems like a lot to read but remember once again, it is only a small part of a letter—Day 26 will help explain some of the imagery here but I wanted you to have an initial read in preparation.)