Preaching from the heart
You do not have to communicate the Word of God merely using your own skills as a communicator. The indwelling Holy Spirit is able to take the sermon you preach and apply it with power and effectiveness to your listeners.
Passionate preaching flows from the heart. To a large degree the modern pulpit is devoid of passion. Few seem to have the element of heart in their preaching styles. We need a return to heart preaching.
Sermons actually are born in the heart. Though the preacher gets his sermon from the Bible, he must bring it to life in his heart. Though he may prepare his message on paper, he must deliver it from his heart. A distinction must be made between the preparation of a sermon and the act of delivering the sermon. A man went to hear George Whitefield preach and asked if he might print his sermons. Whitefield replied, “Well, I have no inherent objection, if you like, but you will never be able to put on the printed page the lightning and the thunder.”
Thus, sermon delivery is not so much the art of delivering a sermon as it is delivering the preacher. The genuinely effective preacher is one who puts everything he has into his sermon. When he speaks, his sincerity and enthusiasm generate sparks. That kind of effectiveness cannot be imitated, for sincerity and earnestness are impossible to manufacture. They come from deep within the heart and spirit of a preacher.
Jerry Vines and Jim Shaddix, Power in the Pulpit: How to Prepare and Deliver Expository Sermons (Chicago, IL: Moody Press, 1999)