I cannot emphasize this enough. The Word of the living God is the source of our messages, and its truths are inexhaustible. There is simply no excuse for a man stepping into the pulpit without having something profound, insightful, and rich to share with his people.
My father is an expositor, and one thing he hammered into me when I was young was the importance of preparation. He told me again and again, “Don’t you ever go into a pulpit unprepared. And if you say ‘The Bible says …’ you make sure to the best of your ability that it truly does say that.” Lack of preparation leads to poor preaching, offends God, and leads people to weakness, not strength.
David C. Deuel, “Expository Preaching from Old Testament Narrative,” in Rediscovering Expository Preaching (Dallas: Word Publishing, 1992), 297.