(19) باب صَوْمِ يَوْمِ عَاشُورَاءَ
This hadith has been narrated by Ibn Bishr with the same chain of transmitters (but with a slight variation) that he (the Holy Prophet) inquired of them (Jews) about it (fasting on the day of 'Ashura).
Reference: Sahih Muslim 1130 b
In-book reference: Book 13, Hadith 163
USC-MSA web (English) reference(deprecated numbering scheme): Book 6, Hadith 2519