Deuteronomy 21:15

Overview - Deuteronomy 21
The expiation of an uncertain murder.
10 The usage of a captive taken to wife.
15 The first-born is not to be disinherited upon private affection.
18 A rebellious son is to be stoned to death.
22 The malefactor must not hang all night on a tree.
Treasury of Scripture Knowledge

Deuteronomy 21:15  (King James Version)
If a man have two wives, one beloved, and another hated, and they have born him children, both the beloved and the hated; and if the firstborn son be hers that was hated:

two wives
Genesis 29:18 Genesis 29:20 Genesis 29:30 Genesis 29:31 Genesis 29:33 ; 1 Samuel 1:4 1 Samuel 1:5