Genesis 38:9-11

Complete Jewish Bible

⁹ However, Onan knew that the child would not count as his; so whenever he had intercourse with his brother’s wife, he spilled the semen on the ground, so as not to give his brother offspring. ¹⁰ What he did was evil from Adonai’s perspective, so he killed him too.

¹¹ Then Y’hudah said to Tamar his daughter-in-law, “Stay a widow in your father’s house until my son Shelah grows up”; for he thought, “I don’t want him to die too, like his brothers.” So Tamar went and lived at home with her father.