During the years when I traveled frequently and stayed in a different city every night, I always scheduled a wake-up call when I checked into a hotel. Along with a personal alarm, I needed a jangling telephone to help get me out of bed and moving in the morning.

The book of Revelation contains a spiritual wake-up call in the apostle John’s letters to the seven churches in the province of Asia. To the church in Sardis he wrote this message from Jesus Himself: “I know your deeds; you have a reputation of being alive, but you are dead. Wake up!…