1151 - Issue: He said: "And if he marries two sisters by lineage or fosterage in one contract, it is invalid. And if he marries them in two contracts, the first is his wife, and the statement [regarding both is the same as the statement] (1) regarding a woman and her paternal aunt, or a woman and her maternal aunt."

The summary of this is that gathering together a woman and her sister, her paternal aunt, or her maternal aunt is prohibited. So whenever (2) he gathers them together, by contracting upon them both at once, the contract is not valid for either of them; because it is not possible to validate it for both of them, and there is no merit of one over the other, so it is rendered void for both, just as if a woman were married to two men. Likewise, if he marries five women in one contract, it is void for all of them for that reason. If he marries them in two contracts, the marriage of the first is valid; because there is no gathering in it, and the marriage of the second is void; because the gathering occurs through it. Therefore, by the contract (3) on the first, the second becomes prohibited, and his contract on her is not valid until the first is separated from him, and her marriage and waiting period (idda) have ceased.

Section: If he marries them in two contracts and does not know which of them was the first, then separation from both of them is incumbent upon him. Ahmad said, regarding a man who married two sisters and does not know which of them he married first: "We separate him from both of them." This is because one of them is prohibited to him, and her marriage is void, and we do not know which one is lawful for him, so they have become confused to him. The marriage of one of them is valid (4), and her separation from him cannot be certain except by divorcing them both, or annulling their marriages, so that became obligatory, just as if two guardians married [the same woman] and it is not known which of them was first. If he wishes to separate from one of them, then renew the contract for the other and keep her, there is no harm in that, whether he does so by drawing lots or without drawing lots. This situation falls into three categories; the first of which is that he has not consummated the marriage with either of them, in which case he may contract with one of them immediately after separating from the other. The second is if he has consummated the marriage with one of them, then if he desires...