What does Revelation chapter 3 mean?
Revelation chapter 2 began a series of messages intended for specific churches in the region of Asia Minor. The first four, already discussed, were Ephesus, Smyrna, Pergamum, and Thyatira. All four of these were commended for certain accomplishments, and all but Smyrna were criticized for certain shortcomings. This chapter completes the messages by speaking to the last three churches: Sardis, Philadelphia, and Laodicea.The church at Sardis is given a positive comment, but that remark is really just a springboard to their criticism by Jesus. This church has a good reputation—this is a good thing—but that reputation doesn't actually match their spiritual state. Jesus warns the church at Sardis to "wake up," and stop resting on their laurels. This church was too proud of their prior accomplishments to diligently work for the good of the Kingdom of God. Still, there are those who have been faithful among the church at Sardis (Revelation 3:1–6).
Philadelphia is one of only two churches, out of seven mentioned, that is not given any particular rebuke from Jesus. Instead, they are praised for their perseverance in the face of dire persecution. Like the church of Smyrna, Philadelphia seems to have been attacked by a specific group of non-believing Jews, referred to as a "synagogue of Satan." In response to this hardship, Jesus reassures them that His return will happen suddenly, and they will be rewarded for their faith (Revelation 3:7–13).
Laodicea has the unfortunate distinction of being the only church which receives no positive commentary, whatsoever. Sardis barely earned a hollow reference to a good reputation. Laodicea is charged with being spiritually inert: lukewarm, rather than either hot or cold. This evokes the disgusting sensation of room-temperature water in one's mouth. Jesus heavily criticized this church for being arrogant and apathetic. Rather than being spiritually passionate, they are passive. Instead of being cold, meaning they are more likely to respond to the gospel, they are just familiar enough with God to brush Him off. Jesus still offers a chance for repentance—but He describes Himself as "outside", knocking at the door and expecting them to answer (Revelation 3:14–22).
This concludes the messages intended for the seven churches in Revelation. The rest of this "revealing" will describe events which, at the time John wrote, were still in the future. These catastrophic moments are what modern people would consider the "end of the world."