If she does not please her master, who has married her to himself, then he must let her be redeemed. He will have no right to sell her to a foreign people, since he has dealt deceitfully with her. Bible see other translations

“then he must let her be redeemed.” If the master married a girl who was sold into slavery, but she did not please him, then the master was to let her birth family buy her back. He could not sell an Israelite girl to a non-Israelite, a foreigner. However, what usually happened was the master would simply take another wife along with the unloved wife (concubine), but since wives cost money and time, he might simply sell the unloved woman back to her family.

Commentary for: Exodus 21:8