What are the virtues of the month of Muharram and fasting 'Aashooraa'?

What are the virtues of the month of Muharram and fasting 'Aashooraa'?

Praise be to Allaah, the Lord of the Worlds, and peace and blessings be upon our Prophet Muhammad, the Seal of the Prophets and Chief of the Messengers, and upon all his family and companions. Allah’s sacred month of Muharram is a blessed and important month. It is the first month of the Hijri calendar and is one of the four sacred months concerning which Allaah says (interpretation of the meaning):
«Verily, the number of months with Allaah is twelve months (in a year), so it was ordained by Allaah on the Day when He created the heavens and the earth; of them, four are sacred. That is the right religion, so wrong not yourselves therein…» [al-Tawbah 9:36]

Abu Bakrah (may Allaah be pleased with him) reported that the Prophet (peace and blessings of Allaah be upon him) said:
‹The year is twelve months of which four are sacred, the three consecutive months of Dhu’l-Qa’dah, Dhu’l-Hijjah and Muharram, and Rajab Mudar which comes between Jumaada and Sha’baan.› (Reported by al-Bukhaari, 2958).

Muharram is so called because it is a sacred (muharram) month and to confirm its sanctity.

Allaah’s words (interpretation of the meaning): “so wrong not yourselves therein…” mean do not wrong yourselves in these sacred months, because sin in these months is worse than in other months.

It was reported that Ibn ‘Abbaas said that this phrase (so wrong not yourselves therein…) referred to all the months, then these four were singled out and made sacred, so that sin in these months is more serious and good deeds bring a greater reward.
Qutaadah said concerning this phrase (so wrong not yourselves therein…) that wrongdoing during the sacred months is more serious and more sinful that wrongdoing at any other time. Wrongdoing at any time is a serious matter, but Allaah gives more weight to whichever of His commands He will. Allaah has chosen certain ones of His creation. He has chosen from among the angels Messengers and from among mankind Messengers. He chose from among speech the remembrance of Him (dhikr). He chose from among the earth the mosques, from among the months Ramadaan and the sacred months, from among the days Friday and from among the nights Laylat al-Qadr, so venerate that which Allaah has told us to venerate. People of understanding and wisdom venerate the things that Allaah has told us to venerate. (Summarized from the Tafseer of Ibn Katheer, may Allaah have mercy on him. Tafseer of Surat al-Tawbah, aayah 36).

The Virtue of observing more naafil fasts during Muharram.

Abu Hurayrah (may Allaah be pleased with him) said: “The Messenger of Allaah (peace and blessings of Allaah be upon him) said: ‘The best of fasting after Ramadaan is fasting Allaah’s month of Muharram.’” (reported by Muslim, 1982).
The phrase “Allaah’s month”, connecting the name of the month to the name of Allaah in a genitive grammatical structure, signifies the importance of the month. Al-Qaari said: “The apparent meaning is all of the month of Muharram.” But it was proven that the Prophet (peace and blessings of Allaah be upon him) never fasted any whole month apart from Ramadan, so this hadeeth is probably meant to encourage increasing one’s fasting during Muharram, without meaning that one should fast for the entire month.
It was reported that the Prophet (peace and blessings of Allaah be upon him) used to fast more in Sha’baan. It is likely that the virtue of Muharram was not revealed to him until the end of his life, before he was able to fast during this month. (Sharh al-Nawawi ‘ala Saheeh Muslim).
Allaah chooses whatever times and places He wills Al-‘Izz ibn ‘Abd al-Salaam (may Allaah have mercy on him) said: “Times and places may be given preferred status in two ways, either temporal or religious/spiritual. With regard to the latter, this is because Allaah bestows His generosity on His slaves at those times or in those places, by giving a greater reward for deeds done, such as giving a greater reward for fasting in Ramadaan than for fasting at all other times, and also on the day of ‘Aashooraa’, the virtue of which is due to Allaah’s generosity and kindness towards His slaves on that day…” (Qawaa’id al-Ahkaam, 1/38).

‘Aashooraa’ in History
Ibn ‘Abbaas (may Allaah be pleased with him) said: “The Prophet (peace and blessings of Allaah be upon him) came to Madeenah and saw the Jews fasting on the day of ‘Aashooraa’. He said, ‘What is this?’ They said, ‘This is a righteous day, it is the day when Allaah saved the Children of Israel from their enemies, so Moosa fasted on this day.’ He said, ‘We have more right to Moosa than you,’ so he fasted on that day and commanded [the Muslims] to fast on that day.” (Reported by al-Bukhaari, 1865).
“This is a righteous day” – in a report narrated by Muslim, [the Jews said:] “This is a great day, on which Allaah saved Moosa and his people, and drowned Pharaoh and his people.”
“Moosa fasted on this day” – a report narrated by Muslim adds:
“… in thanksgiving to Allaah, so we fast on this day.”
According to a report narrated by al-Bukhaari: “… so we fast on this day to venerate it.”
A version narrated by Imaam Ahmad adds: “This is the day on which the Ark settled on Mount Joodi, so Nooh fasted this day in thanksgiving.”
“and commanded [the Muslims] to fast on that day” – according to another report also narrated by al-Bukhaari: “He said to his Companions: ‘You have more right to Moosa than they do, so fast on that day.”
The practice of fasting on ‘Aashooraa’ was known even in the days of Jaahiliyyah, before the Prophet’s mission. It was reported that ‘Aa’ishah (may Allaah be pleased with her) said:
“The people of Jaahiliyyah used to fast on that day…”
Al-Qurtubi said: “Perhaps Quraysh used to fast on that day on the basis of some past law, such as that of Ibraaheem, upon whom be peace.”
It was also reported that the Prophet (peace and blessings of Allaah be upon him) used to fast on ‘Aashooraa’ in Makkah, before he migrated to Madeenah. When he migrated to Madeenah, he found the Jews celebrating this day, so he asked them why, and they replied as described in the hadeeth quoted above. He commanded the Muslims to be different from the Jews, who took it as a festival, as was reported in the hadeeth of Abu Moosa (may Allaah be pleased with him), who said: “The Jews used to take the day of ‘Aashooraa’ as a festival [according to a report narrated by Muslim: the day of ‘Aashooraa’ was venerated by the Jews, who took it as a festival. According to another report also narrated by Muslim: the people of Khaybar (the Jews) used to take it as a festival and their women would wear their jewellery and symbols on that day]. The Prophet (peace and blessings of Allaah be upon him) said: ‘So you [Muslims] should fast on that day.’”
(Reported by al-Bukhaari). Apparently the motive for commanding the Muslims to fast on this day was the desire to be different from the Jews, so that the Muslims would fast when the Jews did not, because people do not fast on a day of celebration. (Summarized from the words of al-Haafiz Ibn Hajar – may Allaah have mercy on him – in Fath al-Baari Sharh ‘ala Saheeh al-Bukhaari).
Fasting on ‘Aashooraa’ was a gradual step in the process of introducing fasting as a prescribed obligation in Islam. Fasting appeared in three forms. When the Messenger of Allaah (peace and blessings of Allaah be upon him) came to Madeenah, he told the Muslims to fast on three days of every month and on the day of ‘Aashooraa’, then Allaah made fasting obligatory when He said (interpretation of the meaning): “… observing the fasting is prescribed for you…” [al-Baqarah 2:183] (Ahkaam al-Qur’aan by al-Jassas, part 1).

The obligation was transferred from the fast of ‘Aashooraa’ to the fast of Ramadaan, and this one of the proofs in the field of Usool al-Fiqh that it is possible to abrogate a lighter duty in favour of a heavier duty. Before the obligation of fasting ‘Aashooraa’ was abrogated, fasting on this day was obligatory, as can be seen from the clear command to observe this fast. Then it was further confirmed later on, then reaffirmed by making it a general command addressed to everybody, and once again by instructing mothers not to breastfeed their infants during this fast. It was reported from Ibn Mas’ood that when fasting Ramadaan was made obligatory, the obligation to fast ‘Aashooraa’ was lifted, i.e., it was no longer obligatory to fast on this day, but it is still desirable (mustahabb).