You can have good preaching even with a poor sermon; it is a real possibility. ... There is the sermon, a sermon which he has prepared; and then there is the 'act' of delivering this sermon. Another way of stating it is this. A man came -- I think it was actually in Philadelphia -- on one occasion to the great George Whitefield and asked if he might print his sermons. Whitefield gave this reply; he said, '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.' That is the distinction -- the sermon, and the 'lightning and the thunder'. To Whitefield this was of very great importance, and it should be of very great importance to all preachers... You can put the sermon into print, but not the lightning and the thunder. That comes into the act of preaching and cannot be conveyed by cold print. Indeed it almost baffles the descriptive powers of the best reporters.
D. Martyn Lloyd-Jones, Preaching and Preachers, pf 58.