Sahih Bukhari 2007

حَدَّثَنَا الْمَكِّيُّ بْنُ إِبْرَاهِيمَ ، حَدَّثَنَا يَزِيدُ بْنُ أَبِي عُبَيْدٍ ، عَنْ سَلَمَةَ بْنِ الْأَكْوَعِ رَضِيَ اللَّهُ عَنْهُ ، قَالَ : أَمَرَ النَّبِيُّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ رَجُلًا مِنْ أَسْلَمَ أَنْ أَذِّنْ فِي النَّاسِ ، أَنَّ مَنْ كَانَ أَكَلَ فَلْيَصُمْ بَقِيَّةَ يَوْمِهِ ، وَمَنْ لَمْ يَكُنْ أَكَلَ فَلْيَصُمْ ، فَإِنَّ الْيَوْمَ يَوْمُ عَاشُورَاءَ .

Narrated Salama bin Al-Akwa`: The Prophet ordered a man from the tribe of Bani Aslam to announce amongst the people that whoever had eaten should fast the rest of the day, and whoever had not eaten should continue his fast, as that day was the day of 'Ashura' .