Er: Son of Judah
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Genesis 38:3, 6, 7
So she conceived and gave birth to a son, and Judah named him Er. / Now Judah acquired a wife for Er, his firstborn, and her name was Tamar. / But Er, Judah’s firstborn, was wicked in the sight of the LORD; so the LORD put him to death.
Genesis 46:12
The sons of Judah: Er, Onan, Shelah, Perez, and Zerah; but Er and Onan died in the land of Canaan. The sons of Perez: Hezron and Hamul.
Numbers 26:19
The sons of Judah were Er and Onan, but they died in the land of Canaan.
1 Chronicles 2:3
The sons of Judah: Er, Onan, and Shelah. These three were born to him by Bath-shua the Canaanite. Er, Judah’s firstborn, was wicked in the sight of the LORD, who put him to death.