Genesis 38:7-9

Lexham English Bible

⁷ And Er, the firstborn of Judah, was evil in the eyes of Yahweh, and Yahweh killed him. ⁸ Then Judah said to Onan, “Go in to the wife of your brother and perform the duty of a brother-in-law to her, and raise up offspring for your brother.” ⁹ But Onan knew that the offspring would not be for him, so whenever he went in to the wife of his brother he would waste it on the ground^[a] so as not to give offspring to his brother.