Sunan an-Nasa'i, Book 22, Hadith 231 (In-Book) ⓘ

It was narrated that Muhammad bin Saifi said: "The Messenger of Allah said on the day of Ashura: Is there anyone among you who has eaten today?' They said: Some of us are fasting and some of us are not.' He said: 'Do not eat for the rest of the day, and send word to the people of Al-Al-Arud telling them not to eat for the rest of the day."'

أَخْبَرَنَا عَبْدُ اللَّهِ بْنُ أَحْمَدَ بْنِ عَبْدِ اللَّهِ بْنِ يُونُسَ أَبُو حَصِينٍ، قَالَ حَدَّثَنَا عَبْثَرٌ، قَالَ حَدَّثَنَا حُصَيْنٌ، عَنِ الشَّعْبِيِّ، عَنْ مُحَمَّدِ بْنِ صَيْفِيٍّ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم يَوْمَ عَاشُورَاءَ ‏"‏ أَمِنْكُمْ أَحَدٌ أَكَلَ الْيَوْمَ ‏"‏ ‏.‏ فَقَالُوا مِنَّا مَنْ صَامَ وَمِنَّا مَنْ لَمْ يَصُمْ ‏.‏ قَالَ ‏"‏ فَأَتِمُّوا بَقِيَّةَ يَوْمِكُمْ وَابْعَثُوا إِلَى أَهْلِ الْعَرُوضِ فَلْيُتِمُّوا بَقِيَّةَ يَوْمِهِمْ ‏"‏ ‏.‏