In the Name of Allâh, the Most Beneficent, the Most Merciful
'Abd-Allaah ibn 'Abbaas (may Allaah be pleased with him) said: When the Messenger of Allaah (peace and blessings of Allaah be upon him) fasted on the day of 'Ashoora and told the people to fast, they said, "O Messenger of Allaah, this is a day that is venerated by the Jews and Christians." The Messenger of Allaah (peace and blessings of Allaah be upon him) said, "Next year, if Allaah wills, we will fast on the ninth day." But by the time the following year came, the Messenger of Allaah (peace and blessings of Allaah be upon him) had passed away.
Narrated by Muslim, 1916.
Al-Shaafa'i and his companions, Ahmad, Ishaaq and others said: It is mustahabb [recommended] to fast both the ninth and the tenth, because the Prophet (peace and blessings of Allaah be upon him) fasted the tenth and intended to fast the ninth.
Based on this, there are different ways of fasting 'Ashoora', the least of which is to fast the tenth only, but it is better to fast the ninth as well. The more one fasts in Muharram, the better.
If one were to ask, what is the wisdom behind fasting the ninth as well as the tenth?
The answer is:
Al-Nawawi (may Allaah have mercy on him) said: The scholars among our companions and others said that there are several reasons for recommending fasting on the ninth day (Tasoo'a'):
1 – The intention behind it is to be different from the Jews who limit their fasting to the tenth day. This was narrated from Ibn 'Abbaas.
2 – The intention was to join the fast of 'Ashoora' to another day, just as it is not allowed to fast on a Friday on its own [but it is allowed if one fasts the day before or the day after as well].
3 – The idea is to be on the safe side and make sure one is fasting on the tenth, in case the moon sighting was not accurate and what people think is the ninth is actually the tenth.
The strongest of these reasons is in order to be different from the People of the Book. Shaykh al-Islam Ibn Taymiyah said: The Prophet (peace and blessings of Allaah be upon him) forbade resembling the People of the Book in many ahaadeeth. For example, he said concerning 'Ashoora': "If I live until next year I will certainly fast the ninth." Al-Fataawa al-Kubra, part 6.
Ibn Hajar (may Allaah have mercy on him) said, commenting on the hadeeth "If I live until next year I will certainly fast the ninth": His concern to fast the ninth may be understood as meaning that he would not limit himself to that, rather that he would add it to the tenth, either to be on the safe side, or to be different from the Jews and Christians, which is more likely to be correct; this is what may be understood from some of the reports narrated by Muslim."
From Fath al-Baari, 4/245.
The virtue of fasting 'Ashoora'
2-Qstn: I heard that fasting the day of 'Ashoora' expiates for the past year, is this true?
Does it expiate for everything, even major sins? What is the reason for venerating this day?.
You can check this link: http://www.islamqa.com/en/ref/21775
Or you can read below
Praise be to Allaah.
Fasting the day of 'Ashoora' does expiate for the past year, because the Prophet (peace and blessings of Allaah be upon him) said: "Fasting the day of 'Arafah I hope Allaah will expiate thereby for the year before it and the year after it, and fasting the day of 'Ashoora' I hope Allaah will expiate thereby for the year that came before it." Narrated by Muslim, 1162. This is by the bounty that Allaah bestows upon us, whereby fasting one day expiates for the sins of a whole year. And Allaah is the Owner of great bounty.
The Prophet (peace and blessings of Allaah be upon him) used to be very keen to make sure he fasted on the day of 'Ashoora' because of its great status. It was narrated that Ibn 'Abbaas (may Allaah be pleased with him) said: I never saw the Prophet (peace and blessings of Allaah be upon him) so keen to make sure he fasted any day and preferring it over another except this day, the day of 'Ashoora', and this month – meaning Ramadaan. Narrated by al-Bukhaari, 1867.
What is meant by being keen to make sure he fasted it is so as to earn its reward.
With regard to the reason why the Prophet (peace and blessings of Allaah be upon him) fasted on the day of 'Ashoora' and urged the people to do likewise is mentioned in the hadeeth narrated by al-Bukhaari (1865) from Ibn 'Abbaas (may Allaah be pleased with him), who said: The Prophet (peace and blessings of Allaah be upon him) came to Madeenah and saw the Jews fasting on the day of 'Ashoora'. He said, "What is this?" They said, "This is a good day, this is the day when Allaah saved the Children of Israel from their enemy and Moosa fasted on this day." He said, "We have closer to Moosa than you." So he fasted on this day and told the people to fast.
The words "this is a good day" – according to a version narrated by Muslim, "This is a great day when Allaah saved Moosa and his people and drowned Pharaoh and his people."
The words "so Moosa fasted on this day" – Muslim added in his report: "In gratitude to Allaah, so that is we fast on this day."
According to another version narrated by al-Bukhaari, "So we fast it out of respect for it."
The words "and told the people to fast" – according to another version narrated by al-Bukhaari, "He said to his companions, 'You are closer to Moosa than them, so fast this day."
The expiation of sins that is achieved by fasting 'Ashoora' refers to minor sins; with regard to major sins, they need separate repentance.
Al-Nawawi (may Allaah have mercy on him) said:
Fasting the day of 'Arafaah expiates for all minor sins, in other words this brings forgiveness for all sins except for major sins.
Then he said:
Fasting the day of 'Arafaah is an expiation for two years, and the day of 'Ashoora is an expiation for one year, and if a person's Ameen coincides with the Ameen of the angels, his previous sins will be forgiven… Each of the things mentioned may bring expiation. If he does something that expiates for minor sins he will be expiated, and if there are no minor or major sins, it will be recorded for him as good deeds and he will rise in status thereby… If there is one or more major sins and no minor sins, we hope that it will reduce his major sins. Al-Majmoo' Sharh al-Muhadhdhab, part 6.
Shaykh al-Islam Ibn Taymiyah (may Allaah have mercy on him) said: The expiation of purification, prayer, and fasting Ramadaan, 'Arafah and 'Ashoora' applies to minor sins only. Al-Fataawa al-Kubra, part 5.
Courtesy : Islam Q&A
May Allah guide us all in the straight Path,Ameen!!!
Jazak Allahu Kharun,