صَحِيحُ مُسْلِمٍ
Sahih Muslim 1446 a
The Book of Suckling
The daughter of one's brother through breastfeeding is forbidden in marriage
حَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، وَزُهَيْرُ بْنُ حَرْبٍ، وَمُحَمَّدُ بْنُ الْعَلاَءِ، - وَاللَّفْظُ لأَبِي بَكْرٍ - قَالُوا حَدَّثَنَا أَبُو مُعَاوِيَةَ، عَنِ الأَعْمَشِ، عَنْ سَعْدِ بْنِ عُبَيْدَةَ، عَنْ أَبِي عَبْدِ الرَّحْمَنِ، عَنْ عَلِيٍّ، قَالَ قُلْتُ يَا رَسُولَ اللَّهِ مَا لَكَ تَنَوَّقُ فِي قُرَيْشٍ وَتَدَعُنَا فَقَالَ " وَعِنْدَكُمْ شَىْءٌ " . قُلْتُ نَعَمْ بِنْتُ حَمْزَةَ . فَقَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " إِنَّهَا لاَ تَحِلُّ لِي إِنَّهَا ابْنَةُ أَخِي مِنَ الرَّضَاعَةِ " .
'Ali (Allah be pleased with him) reported having said this: Messenger of Allah, why is it that you select (your wife) from among the Quraish, but you ignore us (the nearest of the kin)? Thereupon he said: Have you anything for me (a suitable match for me)? I said; Yes, the daughter of Hamza, whereupon Allah's Messenger (ﷺ) said: She is not lawful for me, for she is the daughter of my brother by reason of fosterage.
Sahih Muslim, 1446 aSahihصحيح