Genesis 38:1-10

About this time, Judah left home and moved to Adullam, where he stayed with a man named Hirah. There he saw a Canaanite woman, the daughter of Shua, and he married her. When he slept with her, she became pregnant and gave birth to a son, and he named the boy Er. Then she became pregnant again and gave birth to another son, and she named him Onan. And when she gave birth to a third son, she named him Shelah. At the time of Shelah’s birth, they were living at Kezib. In the course of time, Judah arranged for his firstborn son, Er, to marry a young woman named Tamar. But Er was a wicked man in the LORD’s sight, so the LORD took his life. Then Judah said to Er’s brother Onan, “Go and marry Tamar, as our law requires of the brother of a man who has died. You must produce an heir for your brother.” But Onan was not willing to have a child who would not be his own heir. So whenever he had intercourse with his brother’s wife, he spilled the semen on the ground. This prevented her from having a child who would belong to his brother. But the LORD considered it evil for Onan to deny a child to his dead brother. So the LORD took Onan’s life, too.