Preaching is more than the regurgitation of your favorite exegetical commentary, or a rather transparent recast of the sermons of your favorite preachers, or a reshaping of notes from one of your favorite seminary classes. It is bringing the transforming truths of the gospel of Jesus Christ from a passage that has been properly understood, cogently and practically applied, and delivered with the engaging tenderness and passion of a person who has been broken and restored by the very truths he stands up to communicate. You simply cannot do that without proper preparation, meditation, confession, and worship.
