Leviticus 18:15

Thy daughter-in-law. — The legislators in the time of Christ defined this prohibition as applicable not only to cases where marriage between them had actually been consummated, but to cases where the maiden had only been espoused, or when the daughter-in-law had been divorced by the son, or had become a widow. For an offence of this kind both parties were punished with death. (See Leviticus 20:12.) Other nations regarded such alliances with the same abhorrence. (See Koran, 4:27.)