Muharram – The first month of the Hijra calendar – is one of the four sacred months about which Allah said: “Verily, the number of months with Allah is 12 months (in a year), so it was ordained by Allah 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…” (Qur’an, 9:36)

The Prophet (peace be upon him) said: “The year is 12 months of which four are sacred, the three consecutive months of Dhu’l-Qa’dah, Dhu’l-Hijjah and Muharram, and Rajab which comes between Jumada and Sha’ban.” (Al-Bukhari, 2958)

It was reported that Ibn ‘Abbas 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.

Voluntary fasting
The Messenger of Allah (peace be upon him) said: “The best of fasting after Ramadan is fasting Allah’s month of Muharram.” (Sahih Muslim)

This Hadith is probably meant to encourage fasting during Muharram, without meaning that one should fast for the entire month.

Fasting on ‘Ashoura

Ibn Abbas said: “The Prophet (peace be upon him) came to Madina and saw the Jews fasting on the day of ‘Ashoura. When he asked them about it, they said, ‘This is a blessed day, it is the day when Allah saved the Children of Israel from their enemies, so Musa (peace be upon him) fasted on this day.’ The Prophet (peace be upon him) said, ‘We have more right to Musa (peace be upon him) than you,’ so he fasted on that day and commanded (the Muslims) to fast on that day.” (Al-Bukhari)

Fasting on the day of ‘Ashoura was earlier obligatory, but when fasting Ramadan was made obligatory, the obligation to fast ‘Ashoura was cancelled, i.e., it was no longer obligatory to fast on this day, but it is still recommended.

Virtues of fasting ‘Ashoura
The Prophet (peace be upon him) said: “For fasting the day of ‘Ashoura, I hope that Allah will accept it as expiation for the year that went before.” (Sahih Muslim)

This is from the bounty of Allah towards us. By fasting one day, He expiates our sins for the whole year. And Allah is the Owner of Great Bounty.

Fasting the ninth and tenth
Abdullah Ibn Abbas said: “When the Messenger of Allah (peace be upon him) fasted on ‘Ashoura and commanded the Muslims to fast as well, they said, ‘O Messenger of Allah, it is a day that is venerated by the Jews and Christians.’ The Messenger of Allah (peace be upon him) said, ‘If I live to see the next year, Insha Allah, we will fast on the ninth day too.’ But it so happened that the Messenger of Allah (peace be upon him) passed away before the next year came.” (Sahih Muslim)

Al-Shafi’i and his companions, Ahmad, Ishaq and others said: “It is Mustahab (recommended) to fast on both days, ninth and tenth, because the Prophet (peace be upon him) fasted on the tenth, and intended to fast on the ninth.”