After essentially calling the members of the church in Sardis the "church of the mostly dead," Jesus Christ instructs them to "be watchful." He complements this with, "strengthen the things which remain," which qualifies the meaning of "watch." There is still a glimmer of life within this church, but the letter gives the impression that they have relaxed in their spiritual responsibilities so much that they are nearly comatose. They have not been vigilant in their core responsibilities or on guard against deception, apathy, or neglect. They have not had sleepless nights over their standing with God.
Interestingly, in the Bible's first mention of the Day of the Lord (Isaiah 2:12), it says that it "shall come upon everything proud and lofty, upon everything lifted up—and it shall be brought low." The primary target is the proud—the self-assured. The ironic thing is that this state of spiritual near-death could easily come about even while they are avidly watching world events. They could be quite adept at following the news reports and may know better than anyone what is really going on in the world and how it fits with prophecy.
But that does not fulfill Christ's and the apostle's commands to watch! It is not that it is wrong to keep tabs on world news, but watching world news is chiefly about observing. True watching emphasizes diligence; it is being alert to spiritual dangers more than physical ones. It is about faithfully carrying out our God-given responsibilities, like a servant in the Master's house. None of that results from simply being a news- or prophecy-addict.
In verse 3, He tells them to call to mind the previous lessons and instructions they have heard. He tells them to repent and to guard and maintain their position so they backslide no further. As before, His description gives little indication of spiritual vibrancy or zeal. There probably is a great deal of activity, since He says that they have a name—or reputation—for being alive. Yet, in the areas that truly matter—like growth, faith, seeking God, and overcoming—not much is happening.
He also warns them that, if they will not watch themselves and their covenant responsibilities to their Master, He will come upon them like a thief. He implies that they will not be counted worthy to escape. They may not be appointed to wrath as the world is, but they certainly are not immune to it. In fact, they stand a good chance of experiencing some of it, having not been vigilant and alert in watching over the things that God has given them.
Plainly, Christ will return when we do not expect Him. We may be able to observe some general indicators when key prophecies are fulfilled, but the overall timing will be a mystery. His coming will be like a thief in the night, purposefully hidden from all. Rather than trying to discern the timing, we are instructed to "watch"—not world events, but to watch over all that God has given to us, so that when that Day arrives, we are ready. He knows that if we are faithful in little—in the mundane, the monotonous, the unexciting—we will also be faithful in the truly great things that lie ahead.