From Wayne Grudem’s, Bible Doctrine
Throughout the history of the church the greatest preachers have been those who have recognized that they have no authority in themselves, and have seen their task as being to explain the words of Scripture and apply them clearly to the lives of their hearers. Their preaching has drawn its power not from the proclamation of their own Christian experiences of the experiences of others, nor from their own opinions, creative ideas, or rhetorical skills, but from God’s powerful words. Essentially, they stood in the pulpit, pointed to the biblical text, and said in effect to the congregation, “This is what this verse means. Do you see that meaning here as well? Then you must believe it and obey it with all your heart, for God himself, you Creator and your Lord, is saying this to you today!” Only the written words of Scripture can give this kind of authority to preaching.