Sunan an-Nasa'i #2371 · The Book of Fasting

Sunan an-Nasa'iIt was narrated that Humaid bin 'Abdur-Rahman bin 'Awf said
Sunan an-Nasa'i · Book 22 · The Book of Fasting
Sunan an-Nasa'i · كتاب 22 · كتاب الصيام
"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
أَخْبَرَنَا قُتَيْبَةُ، عَنْ سُفْيَانَ، عَنِ الزُّهْرِيِّ، عَنْ حُمَيْدِ بْنِ عَبْدِ الرَّحْمَنِ بْنِ عَوْفٍ، قَالَ سَمِعْتُ مُعَاوِيَةَ، يَوْمَ عَاشُورَاءَ وَهُوَ عَلَى الْمِنْبَرِ يَقُولُ يَا أَهْلَ الْمَدِينَةِ أَيْنَ عُلَمَاؤُكُمْ سَمِعْتُ رَسُولَ اللَّهِ صلى الله عليه وسلم يَقُولُ فِي هَذَا الْيَوْمِ ‏
"‏ إِنِّي صَائِمٌ فَمَنْ شَاءَ أَنْ يَصُومَ فَلْيَصُمْ ‏"‏ ‏.‏
Reference : Sunan an-Nasa'i 2371In-book reference : Book 22, Hadith 282