Narrated by ‘Aisha :
(The tribe of) Quraish used to fast on the day of Ashura’ in the Pre-lslamic period, and then Allah’s Apostle ordered (Muslims) to fast on it till the fasting in the month of Ramadan was prescribed; whereupon the Prophet said, “He who wants to fast (on ‘Ashura’) may fast, and he who does not want to fast may not fast.”
Volume 3, Book 31, Number 117
Narrated by Ibn ‘Umar :
The Prophet observed the fast on the 10th of Muharram (‘Ashura), and ordered (Muslims) to fast on that day, but when the fasting of the month of Ramadan was prescribed, the fasting of the ‘Ashura’ was abandoned. ‘Abdullah did not use to fast on that day unless it coincided with his routine fasting by chance.
Volume 3, Book 31, Number 116