Genesis 38:2-10

2And Judah saw there the daughter of a Canaanitish man whose name was Shua; and he took her, and went in to her.

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

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

5And again she bore a son, and she called his name Shelah; and he was at Chezib when she bore him.

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

7And Er, Judah's firstborn, was wicked in the sight of Jehovah, and Jehovah slew him.

8Then Judah said to Onan, Go in to thy brother's wife, and fulfil to her the brother-in-law's duty, and raise up seed to thy brother.

9But when Onan knew that the seed should not be his own, it came to pass when he went in to his brother's wife, that he spilled [it] on the ground, in order to give no seed to his brother.

10And the thing which he did was evil in the sight of Jehovah, and he slew him also.