Genesis 38:1-10

And it came to pass at that time, that Judah went down from his brethren, and turned in to a certain Adullamite, whose name was Hirah. And Judah saw there a daughter of a certain Canaanite whose name was Shua; and he took her, and went in unto her. And she conceived, and bare a son; and he called his name Er. And she conceived again, and bare a son; and she called his name Onan. And she yet again bare a son, and called his name Shelah: and he was at Chezib, when she bare him. And Judah took a wife for Er his first-born, and her name was Tamar. And Er, Judah’s first-born, was wicked in the sight of Jehovah; and Jehovah slew him. And Judah said unto Onan, Go in unto thy brother’s wife, and perform the duty of a husband’s brother unto her, and raise up seed to thy brother. And Onan knew that the seed would 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. And the thing which he did was evil in the sight of Jehovah: and he slew him also.