Genesis 38:2-10

2And Judah saw there a daughter of a certain Canaanite whose name was Shua; and he took her, and went in unto her.

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

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

5And she yet again bare a son, and called his name Shelah: and he was at Chezib, when she bare 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 the LORD; and the LORD slew him.

8And Judah said unto Onan, Go in unto thy brother’s wife, and perform the duty of an husband’s brother unto her, and raise up seed to thy brother.

9And Onan knew that the seed should not be his; and it came to pass, when he went in unto his brother’s wife, that he spilled it on the ground, lest he should give seed to his brother.

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