Musnad Ahmad 770
It was narrated that `Alı (رضي الله عنه) said:
When we left Makkah, the daughter of Hamzah followed us, crying: O uncle, O uncle. I took her by the hand and gave her to Fatimah and said: Here is your cousin. When we came to Madinah, Ja`far, Zaid bin Harithah and I disputed concerning her, Ja`far said: She is the daughter of my paternal uncle and her maternal aunt is married to me - meaning Asma’ bint `Umais, Zaid said. She is the daughter of my brother. I said: I took her and she is the daughter of my paternal uncle. The Messenger of Allah (ﷺ) said: “As for you, O Ja`far, you resemble me in appearance and attitude. As for you, O Ali, you are of me and I am of you. As for you, O Zaid, you are our brother and our freed slave. The girl should be with her maternal aunt, for the maternal aunt is [like] a mother.” I said: O Messenger of Allah (ﷺ), why don`t you marry her? He said: `She is the daughter of my brother through breastfeeding.“
حَدَّثَنَا يَحْيَى بْنُ آدَمَ، حَدَّثَنَا إِسْرَائِيلُ، عَنْ أَبِي إِسْحَاقَ، عَنْ هَانِئِ بْنِ هَانِئٍ، وَهُبَيْرَةَ بْنِ يَرِيمَ، عَنْ عَلِيٍّ، رَضِيَ اللَّهُ عَنْهُ قَالَ لَمَّا خَرَجْنَا مِنْ مَكَّةَ اتَّبَعَتْنَا ابْنَةُ حَمْزَةَ تُنَادِي يَا عَمِّ وَيَا عَمِّ قَالَ فَتَنَاوَلْتُهَا بِيَدِهَا فَدَفَعْتُهَا إِلَى فَاطِمَةَ رَضِيَ اللَّهُ عَنْهَا فَقُلْتُ دُونَكِ ابْنَةَ عَمِّكِ قَالَ فَلَمَّا قَدِمْنَا الْمَدِينَةَ اخْتَصَمْنَا فِيهَا أَنَا وَجَعْفَرٌ وَزَيْدُ بْنُ حَارِثَةَ فَقَالَ جَعْفَرٌ ابْنَةُ عَمِّي وَخَالَتُهَا عِنْدِي يَعْنِي أَسْمَاءَ بِنْتَ عُمَيْسٍ وَقَالَ زَيْدٌ ابْنَةُ أَخِي وَقُلْتُ أَنَا أَخَذْتُهَا وَهِيَ ابْنَةُ عَمِّي فَقَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ أَمَّا أَنْتَ يَا جَعْفَرُ فَأَشْبَهْتَ خَلْقِي وَخُلُقِي وَأَمَّا أَنْتَ يَا عَلِيُّ فَمِنِّي وَأَنَا مِنْكَ وَأَمَّا أَنْتَ يَا زَيْدُ فَأَخُونَا وَمَوْلَانَا وَالْجَارِيَةُ عِنْدَ خَالَتِهَا فَإِنَّ الْخَالَةَ وَالِدَةٌ قُلْتُ يَا رَسُولَ اللَّهِ أَلَا تَزَوَّجُهَا قَالَ إِنَّهَا ابْنَةُ أَخِي مِنْ الرَّضَاعَةِ‏.‏