...To cut a long story short, the Lord was displeased with Er, by now a married man, and smote him. And not content with this, He told Onan to go in unto Er's wife and lie with her. Onan, being a decent sort of chap by all accounts, thought this was a bit tough on the widow and, not to put too fine a point on it, spilled his seed upon the ground rather than in his brother's wife. For this refinement of feeling, he too was smitten. So Onan, whatever you may have believed hitherto, was, in fact, a thoroughly moral man and not the wanker everyone thinks he was.
~Margrave of the Marshes, Bantam Press 2005