question #3 Sahih al-Bukhari 7265, Book 95, Hadith 19 : What guidance is provided for those who have not eaten on the day of ‘Ashura’?

Allah’s Messenger (ﷺ) 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.’ ”