(69) باب صِيَامِ يَوْمِ عَاشُورَاءَ
Narrated Abu Musa:
The day of 'Ashura' was considered as `Id day by the Jews. So the Prophet (ﷺ) ordered, "I recommend you (Muslims) to fast on this day."
Reference: Sahih al-Bukhari 2005
In-book reference: Book 30, Hadith 110
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 3, Book 31, Hadith 223