Albert Barnes Commentary Leviticus 19:20

"And whosoever lieth carnally with a woman, that is a bondmaid, betrothed to a husband, and not at all redeemed, nor freedom given her; they shall be punished; they shall not be put to death, because she was not free." — Leviticus 19:20 (ASV)

Betrothed to a husband – Rather, who has been betrothed to a man. The reference appears to be to a bondwoman who has been betrothed to a fellow-servant by her master. Death was the punishment for unfaithfulness in a betrothed woman in other cases .

She shall be scourged – Or, They shall be chastised (see the margin). The trespass-offering was especially due from the man, as he had not only sinned with the woman, but inflicted an injury on the rights of the master.