1 Chronicles 2:3
"The sons of Judah; Er, and Onan, and Shelah: which three were born unto him of the daughter of Shua the Canaanitess. And Er, the firstborn of Judah, was evil in the sight of the LORD; and he slew him."
Cross References (ranked by relevance)
Numbers 26:19
The sons of Judah were Er and Onan: and Er and Onan died in the land of Canaan.
Genesis 46:12
And the sons of Judah; Er, and Onan, and Shelah, and Pharez, and Zarah: but Er and Onan died in the land of Canaan. And the sons of Pharez were Hezron and Hamul.
1 Chronicles 9:5
And of the Shilonites; Asaiah the firstborn, and his sons.