Muwatta Malik, Book 18, Hadith 36 (USC-MSA)

Yahya related to me from Malik from Muhammad ibn Yahya ibn Habban from alAraj from Abu Hurayra that the Messenger of Allah, may Allah bless him and grant him peace, forbade fasting on two days, the day of Fitr and the day of Adha.

حَدَّثَنِي يَحْيَى، عَنْ مَالِكٍ، عَنْ مُحَمَّدِ بْنِ يَحْيَى بْنِ حَبَّانَ، عَنِ الأَعْرَجِ، عَنْ أَبِي هُرَيْرَةَ، ‏.‏ أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم نَهَى عَنْ صِيَامِ يَوْمَيْنِ يَوْمِ الْفِطْرِ وَيَوْمِ الأَضْحَى ‏.‏

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also referenced under: Book 18, Hadith 670 (In-Book)