Genesis 38:8 WEB

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.