Importance of Fasting on the Day of Ashura

What is the importance and virtue of fasting on Ashura Day?

Our Beloved Prophet (pbuh) fasted on the Day of Ashura

Narrated Ibn 'Abbas:

“When the Prophet came to Medina, he found (the Jews) fasting on the day of 'ashura' (i.e. 10th of Muharram). They used to say: "This is a great day on which Allah saved Moses and drowned the folk of Pharaoh. Moses observed the fast on this day, as a sign of gratitude to Allah." The Prophet said, "I am closer to Moses than they." So, he observed the fast (on that day) and ordered the Muslims to fast on it.” (Bukhari; 55; 609)

Ibn Abbas was asked about observing of fast on the day of ashura, whereupon he said: I do not know Allah's Messenger (may peace be upon him) singling out any day's fast and considering it more excellent than another, except this day (the day of ashura) and this month, meaning the month of Ramadan. (Muslim; 6; 2524)

'A'isha (Allah be pleased with her) reported that the Quraish used to fast on the day of 'ashura in the pre-Islamic days and the Messenger ot Allah (may peace be upon him) also observed it. When he migrated to Medina, he himself observed this fast and commanded (others) to observe it. But when fasting during the month of Ramadan was made obligatory he said: He who wishes to observe this fast may do so, and he who wishes to abandon it may do so. (Muslim; 6,2499)

Yahya related to me from Malik from Ibn Shihab that Humayd ibn Abd ar-Rahman ibn Awf heard Muawiya ibn Abi Sufyan say from the mimbar on the day of ashura in the year in which he made the hajj, "People of Madina, where are your learned men? I heard the Messenger of Allah, may Allah bless him and grant him peace, say about this day, 'This is the day of ashura, and fasting it has not been prescribed for you. I am fasting it, and whoever of you wants to fast it can do so, and whoever does not want to, does not have to.' "  (Muwatta 18, 18.11.34)

Prophets fasted on the Day of Ashura

Rasullullah (pbuh) said:

“Fast on the Day of Ashura since it is such a significant day that prophets observed the fast on this day.” (Imam Suyuti)

Sahabas (Companions of the Blessed Prophet) fasted on the Day of Ashura

Narrated Ar-Rubi' bint Mu'awadh:

"The Prophet sent a messenger to the village of the Ansar in the morning of the day of 'ashura' (10th of Muharram) to announce: 'Whoever has eaten something should not eat but complete the fast, and whoever is observing the fast should complete it.' "She further said, "Since then we used to fast on that day regularly and also make our boys fast. We used to make toys of wool for the boys and if anyone of them cried for, he was given those toys till it was the time of the breaking of the fast." (Bukhari; 31;181)

Narrated Salama bin Al-Akwa:

“The Prophet ordered a man from the tribe of Bani Aslam to announce amongst the people that whoever had eaten should fast the rest of the day, and whoever had not eaten should continue his fast, as that day was the day of 'ashura'” (Bukhari; 31;225)

Fasting on the day of ashura' may atone for the sins of the preceding year

“I seek from Allah that fasting on the day of Arafah may atone for the sins of the preceding and the coming year, and I seek from Allah that fasting on the day of ashura' may atone for the sins of the preceding year.” (Abudawud; 13; 2419)