صَحِيحُ مُسْلِمٍ
Sahih Muslim 1130 b
The Book of Fasting
Fasting on the day of Ashura'
وَحَدَّثَنَاهُ ابْنُ بَشَّارٍ، وَأَبُو بَكْرِ بْنُ نَافِعٍ جَمِيعًا عَنْ مُحَمَّدِ بْنِ جَعْفَرٍ، عَنْ شُعْبَةَ، عَنْ أَبِي بِشْرٍ، بِهَذَا الإِسْنَادِ وَقَالَ فَسَأَلَهُمْ عَنْ ذَلِكَ، .
This hadith has been narrated by Ibn Bishr with the same chain of transmitters (but with a slight variation) that he (the Prophet) inquired of them (Jews) about it (fasting on the day of 'Ashura).
Sahih Muslim, 1130 bSahihصحيح