Muwatta Malik, Book 20, Hadith 38 (USC-MSA)

Yahya related to me from Malik, from Abu'l-Aswad Muhammad ibn 'Abd ar-Rahman, from Urwa ibn az-Zubayr, from A'isha, umm al-muminin, that the Messenger of Allah, may Allah bless him and grant him peace, did hajj on its own.

وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ أَبِي الأَسْوَدِ، مُحَمَّدِ بْنِ عَبْدِ الرَّحْمَنِ قَالَ وَكَانَ يَتِيمًا فِي حَجْرِ عُرْوَةَ بْنِ الزُّبَيْرِ عَنْ عُرْوَةَ بْنِ الزُّبَيْرِ عَنْ عَائِشَةَ أُمِّ الْمُؤْمِنِينَ أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم أَفْرَدَ الْحَجَّ ‏.‏

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also referenced under: Book 20, Hadith 745 (In-Book)