“To the angel of the church in Sardis write: These are the words of him who has the seven spirits of God and the seven stars:
“I know your works; you have a name of being alive, but you are dead. Wake up, and strengthen what remains and is on the point of death, for I have not found your works perfect in the sight of my God. Remember then what you received and heard; obey it, and repent. If you do not wake up, I will come like a thief, and you will not know at what hour I will come to you. Yet you have still a few persons in Sardis who have not soiled their clothes; they will walk with me, dressed in white, for they are worthy. If you conquer, you will be clothed like them in white robes, and I will not blot your name out of the book of life; I will confess your name before my Father and before his angels. Let anyone who has an ear listen to what the Spirit is saying to the churches.” (Revelation 3:1–6)
Sardis was built on a mountain and its acropolis was considered impregnable. The phrase, “capturing the acropolis of Sardis” was proverbial in Greek for trying to do the impossible. Even so, it was conquered at least five times thanks to a lack of vigilance on the part of its inhabitants. Thus, Jesus’ warning about its church’s failure to recognize its dangerous situation, was striking. Likewise, Jesus uses the imagery of people not walking with “soiled” clothing and being dressed in white may grow from the fact that the city of Sardis was noted as a center for woolen goods.
In Exodus 32:32, When Moses prayed that God would blot him “out of the book you have written” if God did not forgive the Israelites, God’s response was that only those who had sinned against God would be blotted from his book. Then God “struck the people with a plague.” (Exodus 32:31-35). When Jesus warned the church that if they didn’t repent, they might be blotted from the book of life, he simply meant that they might die. The issue for the people of Sardis was not their place in heaven, but rather their continued chance for life. On occasion, God punishes his people, just as a father punishes his children.
The comfort in the letter is that God is selective in his punishment. He only punishes those who deserve it. For the rest, they will receive God’s blessing.