The second and third chapters of the Book of Revelation are seven letters to seven churches. According to this view, genuine believers are in view and their salvation is not in question. Admittedly, some suggest that since churches sometimes contain unbelievers, then these seven letters may have been addressed to both believers and unbelievers. However, in a biblical sense churches never contain unbelievers. Churches are not buildings or social gatherings.
Churches are assemblies of believers.
Since the Lord was writing to churches, he was writing exclusively to believers. Surely if these seven letters were addressed to unbelievers, we would find repeated calls to trust in Christ. Instead, we find none. Salvation isn't in view in any of those places. Paul was saying that all believers will be raptured, whether they are morally alert or asleep, when Christ returns for them.