“Only the pure in the heart can make a good soup.”

Pearls of Wisdom

"Recent Poetry," The Yale Review (Autumn 1955) [p. 237]
Kipling, Auden & Co: Essays and Reviews 1935-1964 (1980)

The Varieties of Scientific Experience: A Personal View of the Search for God (2006)
Context: The amount of organic matter that could have been produced in the first few hundred million years of Earth history was sufficient to have produced in the present ocean a several-percent solution of organic matter. This is just about the dilution of Knorr's chicken soup, and not that different from the composition either. And chicken soup is widely known to be good for life.

Andrew: On Prostitutes
Jesus, The Son of Man (1928)

Quote in 'Culture: Caspar D. Friedrich and the Wasteland', by Gjermund E. Jansen in Bits of News (3 March 2005) http://www.bitsofnews.com/content/view/154/42/
Variant translation: The heart is the only true source of art, the language of a pure, child-like soul. Any creation not sprung from this origin can only be artifice. Every true work of art is conceived in a hallowed hour and born in a happy one, from an impulse in the artist's heart, often without his knowledge. (as quoted in the article 'Caspar David Friedrich's Medieval Burials', Karl Whittington - http://www.19thc-artworldwide.org/spring12/whittington-on-caspar-david-friedrichs-medieval-burials)
undated
Context: The pure, frank sentiments we hold in our hearts are the only truthful sources of art. A painting which does not take its inspiration from the heart is nothing more than futile juggling. All authentic art is conceived at a sacred moment and nourished in a blessed hour; an inner impulse creates it, often without the artist being aware of it.

Prayer and the Art of Volkswagen Maintenance (2000, Harvest House Publishers)

Variant: the problems of the human heart in conflict with itself which alone can make good writing because only that is worth writing about, worth the agony and the sweat