(70) باب صَوْمِ النَّبِيِّ صلى الله عليه وسلم - بِأَبِي هُوَ وَأُمِّي - وَذِكْرِ اخْتِلاَفِ النَّاقِلِينَ لِلْخَبَرِ فِي ذَلِكَ
It was narrated that Humaid bin 'Abdur-Rahman bin 'Awf said:
"I heard Mu'awiyah say on the day of 'Ashura when he was on the Mindar: O people of Al-Madinah, where are your scholars? I heard the Messenger of Allah say on this day: "I am fasting, so whoever wants to fast let him do so."
Reference: Sunan an-Nasa'i 2371
In-book reference: Book 22, Hadith 282
English translation: Vol. 3, Book 22, Hadith 2373