Genesis 38:1-10

At that time, Judah left his brothers and went down to stay with a man of Adullam named Hirah. There Judah met the daughter of a Canaanite man named Shua. He married her and made love to her; she became pregnant and gave birth to a son, who was named Er. She conceived again and gave birth to a son and named him Onan. She gave birth to still another son and named him Shelah. It was at Kezib that she gave birth to him. Judah got a wife for Er, his firstborn, and her name was Tamar. But Er, Judah’s firstborn, was wicked in the LORD’s sight; so the LORD put him to death. Then Judah said to Onan, ‘Sleep with your brother’s wife and fulfil your duty to her as a brother-in-law to raise up offspring for your brother.’ But Onan knew that the child would not be his; so whenever he slept with his brother’s wife, he spilled his semen on the ground to avoid providing offspring for his brother. What he did was wicked in the LORD’s sight; so the LORD put him to death also.