In the message Jesus sent to the church in Philadelphia, we see one of only two purely positive messages of those he sent to the seven churches. Although the deeds of the Philadelphians are known by him, no correction ensues and no threat follows, only a hopeful promise. Taken together, I think the commendations and rebukes in the Letters to the Churches demonstrate that works do make a difference in how Christ reacts to those who are known by his name. We can infer, thereby, that grace is not something that ignores evidence that reveals that a heart has faith in name only (see James 2:14-26).
For those whose faith is true, Jesus promises to use his key authority to their benefit. He gives a two-fold metric to understand his judgment in the matter: 1) the faithful guard (in the sense that they observe or keep) his word, and 2) the faithful do not deny (disavow or repudiate) his name. In the case of the Philadelphians, both are done in spite of the lack of great ability (dunamis). For the non-charismatic that would probably be taken another way, but for those of us who are charismatic, we could see this as referring to a relative lack of miraculous, spiritual power. Perhaps that is encouraging news to those living in an age where our affirmation for fabulous signs and wonders far outstrips their actual occurrence.
The open door cannot refer to opportunities for gospel work (as so many commentators aver), for that would be a far too pedestrian use of Jesus' keys--particularly since the benefactors experience a lack of power as well as opposition in this world. The open door, therefore, must refer to something in regard to which Christ has unique authority (since none can close what he opens by it). Since these letters have been filled with so many warnings about the things of Christ being closed off to some, context would demand (it seems to me), to see this in regard to all that Christ has been promising by his authority in the midst of these letters. What others written to are shut out from, the Philadelphians are allowed in to.
It is implied in Christ's message to their church, that the faithful Philadelphians were taking some kind of flak from the so-called Synogogue of Satan. That, along with the reference to the Key of David, puts a markedly Jewish spin on this message. That emphasis does not make much sense to me on the basis of anything that occurred in history since the Apocalypse's writing, nor in terms of a framework of historical epochs as some try to apply to these letters. The detail must be significant nonetheless. It is ironic that those of that persuasion (Judaizers, perhaps) were the ones in fact, who will find themselves ostracized by the one who has the Davidic key.
Admittedly, this is an apparent stretch, but this could be referring to a revival of Jewish resistance to the spread of Christianity among the Jews which would occur near the time of the Rapture. We are seeing something akin to that in our own day in the continuing efforts being made in Israel to quell proselytizing among the Jewish population, particularly by Messianic Jews. If so, it will prove to be merely a last ditch effort that will be overwhelmed by the turn of events at the Rapture and God's subsequent redemptive turn toward Israel. I think that could reasonably be described in the terms of the message: "I will make them come and bow down at your feet, and make them know that I have loved you."
Despite that, and whatever other trials they had to get through, the Philadelphians kept Jesus' word of perseverance. The thought conveyed is waiting patiently under command, like the person asked to stay behind for a straggler when the youth group heads out to an event. That Jesus' command to endure (as recorded elsewhere) has eschatological implications cannot be denied--the reference in this letter in conjunction with the promise of escape (rapture) can only underscore the end-times emphasis. What context, other than the end-times, is there for the all-inclusive, global trial mentioned?
It is very difficult to find a context historically which could have justifiably the description of a "global trial" applied to it. The words used to convey the notion of global testing (tou peirasmou [the testing] and peirasai [to test]) are somewhat ambivalent in meaning. They can refer to temptation (as in an enticement), or to trial (as in an assaying pressure), or to both at the same time. The use of the definite article (tou) is supportive in understanding this phrase as referring to a specific testing or temptation, rather than to testing or temptation in general; i.e. the trial. What is in mind in this message, it seems to me, is a singular kind of testing, the scope and nature of which is such that it will leave no doubt that it is occurring when it does occur.
The test will come upon all the inhabited earth to try those that dwell there. Whereas it is possible to see this as an idiomatic reference to the Roman Empire, I see this more along the lines of a Hebraism (e.g. Exodus 8:21) or just straightforwardly referring to the entire world (as does the word's usage in Acts 17:31 or Hebrews 1:6). The inclusivity of the statement means that anyone on earth at that time will experience the trial, at least in some fashion. One would have to not be living on earth to be kept [out] from such a trial, which I think is the best reading of the promise contained: "I also will keep you from the hour of testing..."
Whereas Chapter 7 of the Apocalypse (and Chapter 12 too) does demonstrate that it is possible to live through the trial on earth protected by God in the midst of it, it also reveals (as does Chapter 12) that for the largest proportion of believers, escape means removal from the scene. 1 Thessalonians 4:15-17 describes the escape in as great a detail as we have in all of scripture. Taken together the picture clarifies. A trial, so significant and singular in nature as to be unmistakable, will come upon the entire earth, but those believers, Philadelphian in character, will be kept from that trial by God taking them out from the earth. Rapture!
It is clear to me that the Church in Philadelphia is ultimately a symbol for the church extant and ready when the end comes with its trial of trials. Since it is my belief that the churches which were sent these messages are contemporaneous and representative of different types of the whole, all the churches will be there at the end. However, it is to the church in Philadelphia--the ready church--that promise rather than warning is issued. Those that embrace the promise of removal and overcome get to be with God always, like pillars in his Temple. But even though the letter to the church in Philadelphia is particularly a message to the end-times Church, its message would have been inspirational to any church at any time being stretched by the need to endure under pressure.