Genesis 38:8

5 She yet again bore a son, and named him Shelah: and he was at Chezib, when she bore him.

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

7 Er, Judah`s firstborn, was wicked in the sight of Yahweh. Yahweh killed him.

8 Judah said to Onan, "Go in to your brother`s wife, and perform the duty of a husband`s brother to her, and raise up seed to your brother."

9 Onan knew that the seed wouldn`t be his; and it happened, when he went in to his brother`s wife, that he spilled it on the ground, lest he should give seed to his brother.

10 The thing which he did was evil in the sight of Yahweh, and he killed him also.

11 Then Judah said to Tamar, his daughter-in-law, "Remain a widow in your father`s house, until Shelah, my son, is grown up;" for he said, "Lest he also die, like his brothers." Tamar went and lived in her father`s house.