It is on our knees before the Lord that we can make the [sermon] message our own, possess or re-possess it until it possesses us. Then, when we preach it, it will come neither from our notes, nor from our memory, but out of the depths of our personal conviction, as an authentic utterance of our heart. So, wrote [Richard] Baxter, ‘a minister should take some special pains with his heart before he is to go to the congregation.’ ‘Get you sermon by heart’ pleaded Cotton Mather, meaning not ‘learn it by heart’ but ‘get your heart suitably touched with what you have prepared.’
Every preacher knows the difference between a heavy sermon which trundled along the runway like an overloaded jumbo jet and never gets airborne, and a sermon which has ‘what a bird has, a sense of direction and wings.’ Which kind any sermon will be is usually settled as we pray over it beforehand.
We need to pray till our fresh comes freshly alive to us, the glory shines forth from it, the fire burns in our heart, and we begin to experience the explosive power of God’s Word within us.
—-Between Two Worlds: The Challenge of Preaching Today, p. 257 (line breaks and emphases mine).