J.R. Miller discusses the impact of the gospel during Paul's third missionary journey, particularly in Ephesus, where it clashed with the local economy centered around the worship of Diana. He emphasizes that while the gospel does not inherently oppose business, it does challenge sinful practices that conflict with Christian living. The riot incited by Demetrius highlights how the truth of Christianity can threaten profitable but immoral businesses, leading to opposition from those whose livelihoods depend on such practices. Miller also notes Paul's courage in wanting to defend his companions amidst the chaos, and the importance of having friends who support us in times of need. The sermon concludes with a reminder of the wisdom in the town clerk's advice to avoid rash actions, which can lead to regret and trouble.