The Book of Suckling
17/3. Chapter:
The daughter of one's brother through breastfeeding is forbidden in marriage
Sahih Muslim
وَحَدَّثَنَا هَدَّابُ بْنُ خَالِدٍ، حَدَّثَنَا هَمَّامٌ، حَدَّثَنَا قَتَادَةُ، عَنْ جَابِرِ بْنِ زَيْدٍ، عَنِ ابْنِ، عَبَّاسٍ أَنَّ النَّبِيَّ صلى الله عليه وسلم أُرِيدَ عَلَى ابْنَةِ حَمْزَةَ فَقَالَ " إِنَّهَا لاَ تَحِلُّ لِي إِنَّهَا ابْنَةُ أَخِي مِنَ الرَّضَاعَةِ وَيَحْرُمُ مِنَ الرَّضَاعَةِ مَا يَحْرُمُ مِنَ الرَّحِمِ " .
Ibn Abbas (Allah be pleased with them) reported: It was proposed that he (the Holy Prophet) be married to the daughter of Hamza, whereupon he said: She is not lawful for me for she is the daughter of my foster-brother, and that is unlawful by reason of fosterage what is unlawful by reason of genealogy.
Reference : Sahih Muslim 1447aIn-book reference : Book 17, Hadith 16USC-MSA web (English) reference : Book 8, Hadith 3409