Sahih al-Bukhari 2645
Sahih al-Bukhari · Book 52: Witnesses · To give witness concerning lineage, foster suckling relations and dead persons
Narrated Ibn `Abbas:
حَدَّثَنَا مُسْلِمُ بْنُ إِبْرَاهِيمَ ، حَدَّثَنَا هَمَّامٌ ، حَدَّثَنَا قَتَادَةُ ، عَنْ جَابِرِ بْنِ زَيْدٍ ، عَنِ ابْنِ عَبَّاسٍ ـ رضى الله عنهما ـ قَالَ قَالَ النَّبِيُّ صلى الله عليه وسلم فِي بِنْتِ حَمْزَةَ " لاَ تَحِلُّ لِي، يَحْرُمُ مِنَ الرَّضَاعِ مَا يَحْرُمُ مِنَ النَّسَبِ، هِيَ بِنْتُ أَخِي مِنَ الرَّضَاعَةِ " .
The Prophet (ﷺ) said about Hamza's daughter, "I am not legally permitted to marry her, as foster relations are treated like blood relations (in marital affairs). She is the daughter of my foster brother."