Umm Habiba, the wife of Allah’s Apostle (May peace be upon him), reported that she said to Allah’s Messenger (May peace be upon him): Messenger of Allah, marry my sister ‘Azza, whereupon Allah’s Messenger (May peace be upon him) said: Do you like it? She said: Yes, Messenger of Allah, I am not the exclusive wife of yours, and I wish that the person who joins me in good should be my sister. Thereupon Allah’s Messenger (May peace be upon him) said: That is not lawful for me. I said: Messenger of Allah, we discussed that You intend to marry Durrah bint Abu Salama. He (the Holy Prophet) said: You mean the daughter of Abu Salama? She said: Yes, whereupon Allah’s Messenger (May peace be upon him) said: Even if she were not the step-daughter of mine, brought up under my guardianship, she would not have been lawful for me, for she is the daughter of my foster-brother. Thuwaiba gave me suck and to Abu Salama (also), so do not offer to me your daughters and sisters.
Chapter: It is forbidden to marry the step daughter and the sister of the wife (when the wife is alive and not divorced).