Thanks to Tony Reinke for supplying this quote:
I have a conviction that no sermon is ready for preaching, not ready for writing out, until we can express its theme in a short, pregnant sentence as clear as a crystal. I find the getting of that sentence is the hardest, the most exacting, and the most fruitful labour in my study. To compel oneself to fashion that sentence, to dismiss every word that is vague, ragged, ambiguous, to think oneself through to a form of words which defines the theme with scrupulous exactness—this is surely one of the most vital and essential factors in the making of a sermon: and I do not think any sermon ought to be preached or even written, until that sentence has emerged, clear and lucid as a cloudless moon.”—J. H. Jowett, The Preacher: His Life and Work (Harper & Bros, 1912), p. 133.