ONAN . A son of Judah ( Genesis 38:4; Genesis 46:12 , Numbers 26:19 , 1 Chronicles 2:3 ). After the decease of his elder brother, Er, he was instructed by his father to contract a levirate marriage with Tamar. The device by which he evaded the object of this marriage ‘was evil in the sight of the Lord, and he slew him’ ( Genesis 38:8-10 ).