"She is the daughter of my brother through breast-feeding, and what becomes unlawful (for marriage) through breast-feeding is the same as that which becomes unlawful through lineage." (Using translation from Nasāʾī 3306)
أَنَّ رَسُولَ اللهِ ﷺ أُرِيدَ عَلَى بِنْتِ حَمْزَةَ فَقَالَ «إِنَّهَا لَا تَصْلُحُ لِي إِنَّهَا ابْنَةُ أَخِي مِنَ الرَّضَاعَةِ وَإِنَّهُ يَحْرُمُ مِنَ الرَّضَاعَةِ مَا يَحْرُمُ مِنَ النَّسَبِ»