Deuteronomy 21:14-16

New Revised Standard Version, Anglicised

¹⁴ But if you are not satisfied with her, you shall let her go free and not sell her for money. You must not treat her as a slave, since you have dishonoured her.

The Right of the Firstborn

¹⁵ If a man has two wives, one of them loved and the other disliked, and if both the loved and the disliked have borne him sons, the firstborn being the son of the one who is disliked, ¹⁶ then on the day when he wills his possessions to his sons, he is not permitted to treat the son of the loved as the firstborn in preference to the son of the disliked, who is the firstborn.