Deuteronomy 21:12

8 Accept this atonement, O LORD, for Your people Israel whom You have redeemed, and do not hold the shedding of innocent blood against them.” And the bloodshed will be atoned for.

9 So you shall purge from among you the guilt of shedding innocent blood, since you have done what is right in the eyes of the LORD.

10 When you go to war against your enemies and the LORD your God delivers them into your hand and you take them captive,

11 if you see a beautiful woman among them, and you desire her and want to take her as your wife,

12 then you shall bring her into your house. She must shave her head, trim her nails,

13 and put aside the clothing of her captivity. After she has lived in your house a full month and mourned her father and mother, you may have relations with her and be her husband, and she shall be your wife.

14 And if you are not pleased with her, you are to let her go wherever she wishes. But you must not sell her for money or treat her as a slave, since you have dishonored her.

15 If a man has two wives, one beloved and the other unloved, and both bear him sons, but the unloved wife has the firstborn son,

16 when that man assigns his inheritance to his sons he must not appoint the son of the beloved wife as the firstborn over the son of the unloved wife.

Read all of Deuteronomy 21