Hadith: Even if she was not my stepdaughter whom I raised, she would still be unlawful for me because she is my niece through suckling. Thuwaybah breastfed me and Abu Salāmah (her father). So, do not offer me your daughters or sisters

عن أم حبيبة بنت أبي سفيان رضي الله عنهما قالت: قلت يا رسول الله، انكح أختي ابنة أبي سفيان. قال: أو تحبين ذلك؟ فقلت: نعم؛ لست لك بمُخْلِيَةٍ، وأحَبُّ من شاركني في خير أختي. فقال رسول الله صلى الله عليه وسلم : إن ذلك لا يحل لي. قالت: إنا نُحَدَّثُ أنك تريد أن تنكح بنت أبي سلمة. قال: بنت أم سلمة؟! قالت: قلت: نعم، قال: إنها لو لم تكن ربيبتي في حَجْرِي، ما حلت لي؛ إنها لابنة أخي من الرضاعة، أرضعتني وأبا سلمة ثويبةُ؛ فلا تعرضن علي بناتكن ولا أخواتكن. قال عروة: وثويبة مولاة لأبي لهب أعتقها، فأرضعت النبي صلى الله عليه وسلم ، فلما مات أبو لهب رآه بعض أهله بشرِّ حِيبة، فقال له: ماذا لقيت؟ قال أبو لهب: لم ألق بعدكم خيرًا، غير أني سقيت في هذه بعتاقتي ثويبة.
[صحيح] - [متفق عليه]

Umm Habībah bint Abu Sufyān (may Allah be pleased with her) reported that she said: "O Messenger of Allah, marry my sister, the daughter of Abu Sufyān." He said: "Would you like that?" I said: "Yes, for I cannot have you for myself alone, and I like my sister to be the one who shares with me that goodness." The Messenger of Allah (may Allah's peace and blessings be upon him) said: "That is not lawful for me." She said: "We heard that you want to marry the daughter of Abu Salamah." He said: "The daughter of Umm Salamah?" She said: 'Yes.' He said: "Even if she was not my stepdaughter whom I raised, she would still be unlawful for me because she is my niece through suckling. Thuwaybah breastfed me and Abu Salamah (her father). So, do not offer me your daughters or sisters (in marriage)." ‘Urwah said that Thuwaybah was an emancipated slave girl of Abu Lahab, and she breastfed the Prophet (may Allah's peace and blessings be upon him). When Abu Lahab died, one of his family members saw him in a vision in an awful state. He said to him: "What did you find?" Abu Lahab said: "I found no good after you, except that I have been given water to drink in this (the space between his thumb and other fingers) and that is because of my emancipation of Thuwaybah."
Sahih/Authentic. - [Al-Bukhari and Muslim]

Explanation

Umm Habībah, the daughter of Abu Sufyān, is one of the Mothers of the Believers (may Allah be pleased with them all), and she was ecstatic about her marriage to the Messenger of Allah (may Allah's peace and blessings be upon him). So she asked the Prophet (may Allah's peace and blessings be upon him) to marry her sister. The Prophet (may Allah's peace and blessings be upon him) expressed wonder at her request, due to women’s extreme jealousy regarding the matter, as she would allow herself to have a co-wife. Hence, he asked her in astonishment: Would you like that? And she replied in the affirmative. Then, she explained to him the reason why she wanted him to marry her sister. It was inevitable that she would have to share him with other women and that she would not be his only wife, so she wanted her sister to be the one who would share this great goodness with her . It was as if she was not aware of the prohibition of being married to two sisters at the same time. That is why the Prophet (may Allah's peace and blessings be upon him) informed her that her sister was not lawful for him. Then, she told him that she heard that he would marry the daughter of Abu Salamah. So to be sure, he asked her: Do you mean the daughter of Umm Salamah? She said: Yes. Then, in order to clarify the falsehood of this rumor, he told her that the daughter of Umm Salamah was not lawful for him for two reasons: First: she is his stepdaughter whom he has brought up, because she is his wife’s daughter. Second: she is his niece through suckling, because Thuwaybah, the ex-slave girl of Abu Lahab, had breastfed him and her father Abu Salamah. So, he is her paternal uncle as well. So, he instructed them not offer him their daughters or sisters in marriage, for he knows better how to manage his affairs in this regard.