reported that he heard the Messenger of Allaah 
saying:“Concerning the day of ‘Aashooraa’, it is not obligatory upon you to fast on it as I do. Whoever wishes may fast and whoever does not wish, is not obliged to do so.” [Al-Bukhaari and Muslim]‘Aashooraa’ is the 10th day of Muharram (the first month of the Islamic calendar). There is a great reward in fasting on the day of ‘Aashooraa’. There are many Hadeeths that mention its great virtues. It is highly recommended to fast on this day, although it is not obligatory.
reported that he heard the Messenger of Allaah saying:“Concerning the day of ‘Aashooraa’, it is not obligatory upon you to fast on it as I do. Whoever wishes may fast and whoever does not wish, is not obliged to do so.” [Al-Bukhaari and Muslim]said: "Fasting the day of ‘Aashooraa’ (is of great merits), I hope that Allaah will accept it as an expiation for the previous year.” [Muslim] said: “I never saw Allaah's Messenger so keen to fast any day and give it priority over any other than this day, the day of ‘Aashooraa’ and this month, meaning Ramadhaan.”[Al-Bukhaari] reported: “I asked the Prophet : 'Which prayer is the best after the obligatory prayers?' He said: 'Prayer during the middle of the night.' I asked: 'Which fast is the best after the fast of Ramadhaan?’ He said: 'The month of Allaah that you call Muharram.’” [Muslim, Ahmad and Abu Daawood] sent someone to announce to people that fasting of ‘Aashooraa’ had become voluntary. used to fast on this day with his people in Makkah before the fasting on the month of Ramadhaan was prescribed. When he migrated to Al-Madeenah, he found the Jews fasting on this day. He continued fasting on this day and ordered the Muslims to fast too until it became voluntary. In another report, it is mentioned that Jews of Al-Madeenah used to hold feast on this day. The Prophet told his Companions 
to fast instead. [Al-Bukhaari]
stated: "The tribe of Quraysh used to fast on the day of ‘Aashooraa' in the days before Islam, as did the Prophet . When he came to Madeenah, he still fasted on it and ordered the people to do likewise. Then, when fasting during the month of Ramadhaan became obligatory, he.. said: 'Whoever wishes may fast [‘Aashooraa’] and whoever wishes may leave it.” [Al-Bukhaari and Muslim] came to Madeenah, he found that the Jews of Madeenah observing fasting on this day. The Prophet asked them the reason for their fast. They replied: “This is a blessed day. On this day, Allaah saved Moosa (Moses 
) and the Children of Israel from their enemy and so Prophet Moosa fasted on this day." The Prophet said: "I am worthier of Moosa than you are.” He fasted on that day and commanded the Muslims to fast on that day. [Al-Bukhaari] reported: "The Jews would honor the day of ‘Aashooraa’ as an'Eed (feast). The Prophet said: 'You [Muslims] are to fast on it.’” [Al-Bukhaari and Muslim] observed fast on the same day as the Jews while he previously ordered the Muslims not to follow non-Muslims. According to authentic Hadeeths, the Prophet used to fast on this day even before he emigrated to Madeenah. The Arabs before Islam used to fast on that day and glorified it, and it was the day when they used to cover the Ka'bah. told Muslims to add the 9th day also. If one fasts on this day, it is better to fast the 9th of Muharram or one day before ‘Aashooraa’ (i.e. the 9th) and one after it (i.e. the 11th) to differ from the Jews. said: “Observe fasting on the day of ‘Aashooraa’, but differ from the Jews and fast one day before it and one day after it." [Ahmad] used to say: “We are to fast on two days: the 9th and 10th of Muharram to distinguish ourselves from the Jews.” [At-Tirmithi] also narrated that the Prophet said: “If I live to next year, I shall also fast on the 9th day (as well as the 10th)." [Ahmad] regarding to ‘Aashooraa'. His Companions and their followers went on this way. The Prophet and the Companions and Muslim scholars have not distinguished this day by any practice except fasting.