Exodus 21:8

If she please not her master, who hath betrothed her to himself, then shall he let her be redeemed: to sell her unto a strange nation he shall have no power, seeing he hath dealt deceitfully with her.

Cross-reference

Deuteronomy 21:11-14 is a parallel law: a captive wife no longer delighted in must be freed, not sold. Reinforces the prohibition on selling a rejected wife.