Mas'ud. Among those who stated it is prohibited are Ubayd Allah ibn Abd Allah ibn Utbah, Jabir ibn Zayd, Tawus, Malik, al-Awza'i, Abu Hanifah, and al-Shafi'i. It is reported from Ibn Abbas that he said: "A verse permitted them, and a verse prohibited them, and I would not do so." This is also narrated from Ali. By the prohibiting [verse], he means the saying of the Almighty: "And that you combine two sisters [in marriage]" (Quran 4:23). And by the permitting [verse], he means the saying of the Almighty: "Except for their wives or those their right hands possess" (Quran 23:6). Ibn Mansur narrated from Ahmad that he asked him about combining two sister-slave girls: "Is it haram?" He said: "I do not say it is haram, but we forbid it." The manifest meaning of this is that it is disliked (makruh) but not forbidden (muharram). Dawud and the Zahiris said: "It is not forbidden," relying on the permitting verse, because the ruling of free women regarding intercourse is different from the ruling of slave girls. For this reason, exceeding four is forbidden for free women but permitted for slave girls without limitation. The madhhab [Hanbali school] holds that it is forbidden due to the prohibiting verse, for he intends by it both intercourse and marriage alike, as evidenced by the fact that the rest of the women mentioned in the verse have their intercourse and marriage prohibited, and the verse of permission is specified by all the prohibited women, and these are among them. Furthermore, because she has become a bed (firaash), her sister is prohibited, just like a wife.

Section Three: If there are two sisters in his possession, he may have intercourse with one of them according to the opinion of the majority of scholars. Al-Hakam and Hammad said: "He shall not approach either of them." This is also reported from al-Nakha'i, and Abu al-Khattab mentioned it as a position of Ahmad. Our [argument] is that he is not combining them in the bed, so it is not prohibited, just as if he only had one of them in his possession.