In Genesis 38:3-10, the account of Onan, son of Judah, unfolds with Shua, Judah's wife, bearing a son named Er, and then another son named Onan. Judah took a wife for Er, named Tamar, but Er was wicked in the sight of the LORD, and the LORD killed him. Judah then instructed Onan to marry Tamar and raise up an heir for his brother. However, Onan knew the heir would not be his own, so when he went in to his brother's wife, he emitted on the ground to avoid giving an heir to his brother. This act displeased the LORD, and therefore He killed Onan as well. The LORD's anger toward Onan stemmed from his contemptuous refusal to fulfill his familial responsibility under the Old Covenant through the practice of levirate marriage, which aimed to preserve tribal inheritance rights by having a close male relative marry the widow to produce an heir for the deceased.