Genesis 38:9-11

But Onan knew that the offspring would not be his. So whenever he went in to his brother’s wife he would waste the semen on the ground, so as not to give offspring to his brother. And what he did was wicked in the sight of the LORD, and he put him to death also. Then Judah said to Tamar his daughter-in-law, “Remain a widow in your father’s house, till Shelah my son grows up”—for he feared that he would die, like his brothers. So Tamar went and remained in her father’s house.