Zac Poonen preaches on the message to the church in Philadelphia, emphasizing the significance of Jesus as the holy and true One with the key of David, who opens doors no one can shut. He highlights the importance of holiness and authenticity in believers, pointing to Jesus as the ultimate example of overcoming sin and Satan. Poonen stresses that as followers of Christ, we must trust in God to open the right doors for us and close those that lead us astray, illustrating this with the story of Jonah. He commends the church in Philadelphia for their obedience and perseverance, assuring them of God's protection during trials and encouraging them to hold fast to their faith until His return.