Musnad Ahmad 1169
It was narrated that Abu `Awn said:
I heard Abu Salih say: ‘Ali (رضي الله عنه) said: I mentioned the daughter of Hamzah (as a potential spouse) to the Messenger of Allah (ﷺ) and he said: `She is the daughter of my brother through breastfeeding.`
حَدَّثَنَا مُحَمَّدُ بْنُ جَعْفَرٍ، حَدَّثَنَا شُعْبَةُ، عَنْ أَبِي عَوْنٍ، قَالَ سَمِعْتُ أَبَا صَالِحٍ، قَالَ قَالَ عَلِيٌّ ذَكَرْتُ ابْنَةَ حَمْزَةَ لِرَسُولِ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ فَقَالَ إِنَّهَا ابْنَةُ أَخِي مِنْ الرَّضَاعَةِ‏.‏