Genesis 38:8-10

New Revised Standard Version, Anglicised Catholic Edition

⁸ Then Judah said to Onan, ‘Go in to your brother’s wife and perform the duty of a brother-in-law to her; raise up offspring for your brother.’ ⁹ But since Onan knew that the offspring would not be his, he spilled his semen on the ground whenever he went in to his brother’s wife, so that he would not give offspring to his brother. ¹⁰ What he did was displeasing in the sight of the Lord, and he put him to death also.