Unbelievable.
(1) Odin was the Scandinavian god of the sky.
(2) Onan was one of the very few people in history that God killed with His own hand using no intermediary.
(3) Onan's sin was to deliberately turn a natural act of intercourse into an unnatural one.
(4) How can a duty be not required?
(5) The law of levirate marriage (marrying one's deceased brother's wife to provide offspring in his name) was a duty and its violation was not punishment with death. The punishment for failing to consummate levirate marriage was to be publicly insulted by the wife of one's deceased brother.
(6) God killed Onan because he turned natural intercourse into unnatural. By the way, God also destroyed Sodom for unnatural intercourse. And God also mandated capital punishment in the Levitical law code for a number of the most heinous acts of unnatural intercourse.
(7) If you are completely unfamiliar with the actual text of the Scripture as written, why should we trust your invented-on-the-spot exegesis?
Like I said if you want to condemn the act Onan is commonly accused of doing, look at the teaching of Jesus and adultery of the heart. The act it self is not wrong, it is what accompanies the act.
Say what? His sin was disobiedence because he was told to give his brothers wife a child. Had he done the required deed and later spilled his seed in a river afterward it would have not mattered. Spilling hisd seed on the ground was not the sin. Refusing to do as he was told however was please learn the huge difference.