Deuteronomy 21:13

When you go out to battle against your enemies, and the LORD your God delivers them into your hands and you carry them away captive,

and see among the captives a beautiful woman, and you are attracted to her, and desire to take her as your wife,

then you shall bring her home to your house. She shall shave her head and trim her nails.

It shall be, if you have no delight in her, then you shall let her go where she desires; but you shall not sell her at all for money. You shall not deal with her as a slave, because you have humbled her.

If a man has two wives, the one beloved and the other hated, and they have borne him children, both the beloved and the hated, and if the firstborn son is hers who was hated,

then it shall be, in the day that he causes his sons to inherit that which he has, that he may not give the son of the beloved the rights of the firstborn before the son of the hated, who is the firstborn;