As a former missionary, I’ve preached a lot of sermons on the Great Commission. Jesus famously called His disciples to, “Go therefore and make disciples of all nations” (Matthew 28:18). Those words have inspired Christians to take the good news of the gospel around the world. As urgently as I feel the need to share the good news with people at the ends of the earth, I fear that many Christians don’t even share their faith within the walls of their own church. Let me explain.