Genesis 38:8-10

King James Version

⁸ And Judah said unto Onan, Go in unto thy brother's wife, and marry her, and raise up seed to thy brother.

⁹ And 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 that he should give seed to his brother.

¹⁰ And the thing which he did displeased the Lord: wherefore he slew him also.