1,505. Effecting Marriage with Mutually-Exclusive Women
Hilchos Ishus 9:1
If a man simultaneously consecrates two women to whom he may not be married because it creates a prohibited relationship, marriage is not effected with either of them. Therefore, if a man consecrates a mother and daughter or two sisters simultaneously, neither woman is consecrated.
Hilchos Ishus 9:2
Let’s say that a man consecrates many women simultaneously, saying, “All of you are consecrated to me.” If the group of women includes two sisters, a mother and daughter, or some such pair, then none of the women are consecrated. If he said, “Those of you who are permitted to have marital relations with me are consecrated to me,” then all of them are consecrated to him except for those whose presence excludes one another. Similarly, if he said, “All of you are consecrated to me” and these group includes a Canaanite servant woman, a non-Jewish woman or a woman who is prohibited as one of the forbidden relationships, like a married woman, his daughter, his sister, etc. – in such a case, none of the women are consecrated to him. If he says, “Those of you who are permitted to have marital relations with me are consecrated to me,” then all of them are consecrated to him except for those he is forbidden to marry.