Only a few people in the Sardis church are spiritually alive, walking with Jesus with pure hearts. The only hope for the others is to wake up, remember what they have been taught, and repent of their sin.
Jesus has only commendation for the saints in Philadelphia. They have kept Jesus' Word, have not denied His Name, and have kept His command to endure patiently. Upon them He will write the names of God and the new Jerusalem, and His new name.