صَحِيحُ مُسْلِمٍ
Sahih Muslim 1127 b
The Book of Fasting
Fasting on the day of Ashura'
وَحَدَّثَنَا زُهَيْرُ بْنُ حَرْبٍ، وَعُثْمَانُ بْنُ أَبِي شَيْبَةَ، قَالاَ حَدَّثَنَا جَرِيرٌ، عَنِ الأَعْمَشِ، بِهَذَا الإِسْنَادِ وَقَالاَ فَلَمَّا نَزَلَ رَمَضَانُ تَرَكَهُ .
This hadith has been narrated from Jarir on the authority of A'mash with the same chain of transmitters and he said (these words with a little bit of variation from the previous hadith): When (fasting) in Ramadan was (made) obligatory, he abandoned it (the practice of observing fast on Ashura).
Sahih Muslim, 1127 bSahihصحيح