Musnad Ahmad 1358
It was narrated that ‘Ali (رضي الله عنه) said:
I said: O Messenger of Allah (ﷺ), why do you marry from Quraish and you do not marry from among us? He said: `Do you have anyone” I said: Yes, the daughter of Hamzah. He said: `She is the daughter of my brother through breastfeeding.`
حَدَّثَنَا مُحَمَّدُ بْنُ عُبَيْدٍ، حَدَّثَنَا الْأَعْمَشُ، عَنْ سَعْدِ بْنِ عُبَيْدَةَ، عَنْ أَبِي عَبْدِ الرَّحْمَنِ، عَنْ عَلِيٍّ، رَضِيَ اللَّهُ عَنْهُ قَالَ قُلْتُ يَا رَسُولَ اللَّهِ مَا لَكَ تَنَوَّقُ فِي قُرَيْشٍ وَلَا تَزَوَّجُ إِلَيْنَا قَالَ وَعِنْدَكَ شَيْءٌ قَالَ قُلْتُ نَعَمْ ابْنَةُ حَمْزَةَ قَالَ تِلْكَ ابْنَةُ أَخِي مِنْ الرَّضَاعَةِ‏.‏