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‘Ali said, “Messenger of God, would you like the daughter of your paternal uncle Hamza, for she is the most beautiful girl in Quraish?” He replied, “Do you not know that Hamza is my foster-brother, and that God has prohibited by reason of fosterage what He has prohibited by reason of genealogy?” Muslim transmitted it.
Source: sunnah.com
Other translations
Arabic
وَعَنْ عَلِيٍّ رَضِيَ اللَّهُ عَنْهُ قَالَ: يَا رَسُولَ اللَّهِ هَلْ لَكَ فِي بِنْتِ عَمِّكَ حَمْزَةَ؟ فَإِنَّهَا أَجْمَلُ فَتَاةٍ فِي قُرَيْشٍ فَقَالَ لَهُ: «أَمَا عَلِمْتَ أَنَّ حَمْزَةَ أَخِي مَنِ الرَّضَاعَةِ؟ وَأَنَّ اللَّهَ حَرَّمَ مِنَ الرَّضَاعَةِ مَا حرم من النّسَب؟» . رَوَاهُ مُسلم
sunnah.com