Revelation 3:9 Indeed I will make those of the synagogue of Satan, who say they are Jews and are not, but lie–indeed I will make them come and worship before your feet, and to know that I have loved you.
It would seem that the Philadelphian church was contending with the same synagogue that persecuted Smyrna. The pair of churches have two things in common. First, the Lord has nothing negative or detracting to comment regarding their corporate worship and evangelization.