The Prophet Married Two Half-Sisters: Zaynab bint Khuzaymah and Maymoonah bint Al-Harith
3-5-2017 | IslamWeb
Question:
Is it permissible for a man to marry two half-sisters at the same time? And if this is not permissible, then how did the Prophet, sallallaahu ‘alayhi wa sallam, marry Maymoonah bint Al-Harith and her sister Zaynab bint Khuzaymah?
Answer:
All perfect praise be to Allah, the Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
It is not permissible for a man to combine two full sisters or foster sisters as wives at the same time, as revealed in a verse on the categories of women that a man is prohibited from marrying. Allah Almighty says (what means): {...and that you take [in marriage] two sisters simultaneously...} [Quran 4:23] This is a point of consensus among the scholars.
It is permissible, however, for a man who divorces a woman, after she completes her ‘iddah, or whose wife dies to marry her sister.
This is what the Prophet, sallallaahu ‘alayhi wa sallam, did. He married Zaynab bint Khuzaymah ibn Al-Harith Al-Hilaliyyah in Ramadan, in the 31st month after Hijrah (emigration). She died eight months later, at the end of Rabee‘ Al-Awwal, at the beginning of the 39th month after Hijrah. Al-Qurtubi 
mentioned this in his Tafseer (exegesis). Then he, sallallaahu ‘alayhi wa sallam, married her sister from the mother's side, Maymoonah bint Al-Harith Al-Hilaliyyah, as mentioned by Ibn Hajar in Al-Isabah. Al-Qurtubi said, "He married her in Sarif, ten miles away from Makkah, in 7 A.H., in the compensatory ‘Umrah.
By saying this, the matter becomes clear and there is no longer confusion about any apparent contradiction.
Allah knows best.