Genesis 38:2-10

2There Judah met the daughter of a Canaanite man whose name was Shua. He married her and slept with her.

3She became pregnant and gave birth to a son named  Er.

4She became pregnant again and gave birth to another son, whom she named Onan.

5Then she became pregnant again and gave birth to another son, whom she named Shelah. He was born at Kezib.

6Judah chose a wife for his firstborn son Er. Her name was Tamar.

7Er angered the Lord. So the Lord took away his life.

8Then Judah said to Onan, “Go sleep with your brother’s widow. Do your duty for her as a brother-in-law, and produce a descendant for your brother.”

9But Onan knew that the descendant wouldn’t belong to him, so whenever he slept with his brother’s widow, he wasted his semen on the ground to avoid giving his brother a descendant.

10What Onan did angered the Lord so much that the Lord took away Onan’s life too.