Genesis 38:2-10

2There Judah saw the daughter of a certain Canaanite whose name was Shua. He took her and went in to her,

3and she conceived and bore a son, and he called his name Er.

4She conceived again and bore a son, and she called his name Onan.

5Yet again she bore a son, and she called his name Shelah. Judah was in Chezib when she bore him.

6And Judah took a wife for Er his firstborn, and her name was Tamar.

7But Er, Judah's firstborn, was wicked in the sight of the Lord, and the Lord put him to death.

8Then Judah said to Onan, "Go in to your brother's wife and perform the duty of a brother-in-law to her, and raise up offspring for your brother."

9But 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.

10And what he did was wicked in the sight of the Lord, and he put him to death also.