And the thing which he did was evil in the sight of the LORD; and He slew him also.
King James Version (KJV) - Genesis 38:10 >And the thing which he did displeased the LORD: wherefore he slew him also.
Berean Study Bible (BSB) - Genesis 38:10 >What he did was wicked in the sight of the LORD, so He put Onan to death as well.