Genesis 38:1-10

Around that time, Judah left his brothers at Hebron and went to Adullam to stay with a man named Hirah. There he met and married a Canaanite girl, the daughter of Shua. He slept with her and she became pregnant and gave birth to a son, and Judah named him Er. She conceived again and gave birth to another son and named him Onan. While they were staying in Chezib, she gave birth to a third son and named him Shelah. When their sons were grown, Judah arranged for Er, his oldest son, to marry a girl named Tamar. But Er had become so wicked in the sight of YAHWEH that YAHWEH ended his life. Then Judah said to Er’s brother Onan, “Your duty is to join yourself to her. Go perform your duty as a brother-in-law and provide an heir for your brother.” Onan, however, did not want to produce a child that would not be his own rightful heir, so whenever he and Tamar had intercourse, he purposely spilled his semen onto the ground to keep her from getting pregnant and having a child that would belong to his dead brother. But what he did was wicked in YAHWEH’s sight, so he took Onan’s life also.