Leviticus 19:20

And whosoever lieth carnally with a woman, that is a bondmaid, betrothed to an husband, and not at all redeemed, nor freedom given her; she shall be scourged; they shall not be put to death, because she was not free.

Cross-reference

Deuteronomy 22:23 gives a parallel law for a free betrothed virgin, contrasting with the slave woman here.

Deuteronomy 22:24 prescribes death for a free betrothed woman, directly contrasting the spared slave here.