Sahih Bukhari 7265

حَدَّثَنَا مُسَدَّدٌ ، حَدَّثَنَا يَحْيَى ، عَنْ يَزِيدَ بْنِ أَبِي عُبَيْدٍ ، حَدَّثَنَا سَلَمَةُ بْنُ الْأَكْوَعِ ، أَنَّ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ ، قَالَ لِرَجُلٍ مِنْ أَسْلَمَ : أَذِّنْ فِي قَوْمِكَ ، أَوْ فِي النَّاسِ يَوْمَ عَاشُورَاءَ أَنَّ مَنْ أَكَلَ فَلْيُتِمَّ بَقِيَّةَ يَوْمِهِ ، وَمَنْ لَمْ يَكُنْ أَكَلَ فَلْيَصُمْ .

Narrated Salama bin Al-Akwa`: Allah's Apostle said to a man from the tribe of Al-Aslam, Proclaim among your people (or the people) on the day of 'Ashura' (tenth of Muharram), 'Whosoever has eaten anything should fast for the rest of the day; and whoever has not eaten anything, should complete his fast.'