كتاب الصيام
13
The Book of Fasting
(19)
Chapter: Fasting on the day of Ashura'
(19)
باب صَوْمِ يَوْمِ عَاشُورَاءَ ‏‏

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 aban- doned it (the practice of observing fast on Ashura).
وَحَدَّثَنَا زُهَيْرُ بْنُ حَرْبٍ، وَعُثْمَانُ بْنُ أَبِي شَيْبَةَ، قَالاَ حَدَّثَنَا جَرِيرٌ، عَنِ الأَعْمَشِ، بِهَذَا الإِسْنَادِ وَقَالاَ فَلَمَّا نَزَلَ رَمَضَانُ تَرَكَهُ ‏.‏
Reference : Sahih Muslim 1127 b
In-book reference : Book 13, Hadith 155
USC-MSA web (English) reference : Book 6, Hadith 2511
  (deprecated numbering scheme)