Hadith 2430
Chapter 84: Mentioning The Differences Reported From Musa Bin Talhah In The Narration About Fasting three days of each month - كتاب الصيام
أَخْبَرَنَا مُحَمَّدُ بْنُ عَبْدِ الأَعْلَى، قَالَ حَدَّثَنَا خَالِدٌ، عَنْ شُعْبَةَ، قَالَ أَنْبَأَنَا أَنَسُ بْنُ سِيرِينَ، عَنْ رَجُلٍ، يُقَالُ لَهُ عَبْدُ الْمَلِكِ يُحَدِّثُ عَنْ أَبِيهِ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم كَانَ يَأْمُرُ بِهَذِهِ الأَيَّامِ الثَّلاَثِ الْبِيضِ وَيَقُولُ " هُنَّ صِيَامُ الشَّهْرِ " .
It was narrated that a man called 'Abdul-Malik narrated from his father, that:
the Messenger of Allah used to enjoin (fasting) these days of Al-Bid and he said: "That is (equivalent to) fasting for the whole month."
Reference : Sunan an-Nasa'i 2430
In-book reference : Book 22, Hadith 341