Genesis 38:8-11

8Then Judah said to Onan, “Have sexual relations with your brother’s wife and fulfill the duty of a brother-in-law to her so that you may raise up a descendant for your brother.”

9But Onan knew that the child would not be considered his. So whenever he had sexual relations with his brother’s wife, he withdrew prematurely so as not to give his brother a descendant.

10What he did was evil in the Lord’s sight, so the Lord killed him too.

11Then Judah said to his daughter-in-law Tamar, “Live as a widow in your father’s house until Shelah my son grows up.” For he thought, “I don’t want him to die like his brothers.” So Tamar went and lived in her father’s house.