The Prophet ﷺ 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' .
أَمَرَ النَّبِيُّ ﷺ رَجُلاً مِنْ أَسْلَمَ أَنْ أَذِّنْ فِي النَّاسِ أَنَّ مَنْ كَانَ أَكَلَ فَلْيَصُمْ بَقِيَّةَ يَوْمِهِ وَمَنْ لَمْ يَكُنْ أَكَلَ فَلْيَصُمْ فَإِنَّ الْيَوْمَ يَوْمُ عَاشُورَاءَ