IDLENESS, n. A model farm where the devil experiments with seeds of new sins and promotes the growth of untried vices.
Ambrose Bierce (1842-1914?) American writer and journalist
“Idleness,” The Cynic’s Word Book (1906)
(Source)
Included in The Devil's Dictionary (1911). Originally published in the "Devil's Dictionary" column in the San Francisco Wasp (1885-08-29).