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.' "
— Sahih Bukhari, Volume 9, Book 91: Accepting Information Given by a Truthful Person, Hadith #370
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.' "
This hadith is from the book of Accepting Information Given by a Truthful Person in Sahih Bukhari, compiled by Imam al-Bukhari. It is hadith number 370 in book 91 of volume 9.
