Deuteronomy 21:13

10 When thou goest forth to war against thine enemies, and the LORD thy God hath delivered them into thine hands, and thou hast taken them captive,

11 And seest among the captives a beautiful woman, and hast a desire unto her, that thou wouldest have her to thy wife;

12 Then thou shalt bring her home to thine house; and she shall shave her head, and pare her nails;

13 And she shall put the raiment of her captivity from off her, and shall remain in thine house, and bewail her father and her mother a full month: and after that thou shalt go in unto her, and be her husband, and she shall be thy wife.

14 And it shall be, if thou have no delight in her, then thou shalt let her go whither she will; but thou shalt not sell her at all for money, thou shalt not make merchandise of her, because thou hast humbled her.

15 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:

16 Then it shall be, when he maketh his sons to inherit [that] which he hath, [that] he may not make the son of the beloved firstborn before the son of the hated, [which is indeed] the firstborn: