Genesis 38:9-11

New International Version - UK

⁹ 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. ¹⁰ What he did was wicked in the Lord’s sight; so the Lord put him to death also.

¹¹ Judah then said to his daughter-in-law Tamar, ‘Live as a widow in your father’s household until my son Shelah grows up.’ For he thought, ‘He may die too, just like his brothers.’ So Tamar went to live in her father’s household.