The first month of the Hijri calendar is the month of Muharram which is one of the four sacred months.
{Indeed, the number of months with Allah is twelve (lunar) months in the register of Allah (from) the day He created the heavens and the earth; of these, four are sacred. That is the correct religion, so do not wrong yourselves during them. And fight against the disbelievers collectively as they fight against you collectively. And know that Allah is with the righteous (who fear Him)}. (Chapter 9, verse 36)
Abu Bakr reported that Prophet Muhammad (peace be upon him) said, “The year is 12 months of which four are sacred, the three consecutive months of Dhu al-Qa’dah, Dhu al-Hijjah and Muharram, and Rajab, which comes between Jumada al-Akhirah and Shaban.” (Al-Bukhari)
The 10th day of Muharram, the day of Ashura (means tenth in Arabic) is a significant day for all Muslims. On this day of Ashura Allah accepted the repentance of Adam after his exile from Paradise. Allah saved Prophet Nuh and his believing companions in the ark on this day. Also, it is the day when Allah saved Prophet Musa from his enemies; Pharaoh and his army.
The companion of the Prophet, Ibn Abbas, said, “The Prophet (peace be upon him) came to Madinah and saw the Jews fasting on the day of Ashura. He said, ‘What is this?’ They said, ‘This is a righteous day, it is the day when Allah saved the Children of Israel from their enemies, so Musa fasted on this day.’ He said, ‘We have more right to Musa than you,’ so he fasted on that day and commanded (the Muslims) to fast on that day.” (Sahih Al-Bukhari)
Fasting on Ashura, expiates for the sins of the past year.
As it is obligatory for all Muslims to fast during the month of Ramadan, we are recommended to practice some other voluntary fasts during the year, such as fasting the 13th, 14th and 15th days of the lunar months. Fasting on the day of Arafat and fasting on the tenth of Muharram, along with fasting a day before and a day after the tenth, are among the best types of voluntary fasting.
Abu Hurairah, the well-known companion of the Prophet (peace be upon him) said, “The Messenger of Allah said, “The best of fasting after Ramadan is fasting Allah’s month of Muharram.” (Muslim)
Therefore, fasting during the month of Muharram is highly recommended in Islam. For this reason, fasting on the Day of Ashura is greatly rewarded because first it falls in the month of Muharram and second it has a special significance.
Prophet Muhammad (peace be upon him) said, “Fasting the day of Ashura (is of great merits). I hope that Allah will accept it as an expiation for (the sins committed in) the previous year.” (Sahih Muslim and Sahih Al-Bukhari)
Ibn Abbas reported that Prophet Muhammad (peace be upon him) said, “I never saw the Prophet more keen to fast on any day other than the day of Ashura and any month than the month of Ramadan.” (Sahih Al-Bukhari)
Muawiyah ibn Abu Sufyan said, “I heard the Messenger of Allah (peace be upon him) say: ‘It is the day of Ashura. Allah has not made fasting obligatory for you. But I am fasting. He who likes to observe fast among you should do so, and he who likes not to observe it, does not have to observe it.’” (Sahih Muslim)
Fasting on Ashura was a gradual step in the process of introducing fasting as a prescribed obligation in Islam and the fourth pillar of Islam. Fasting appeared in three forms. When the Messenger of Allah (peace be upon him) came to Madinah, he told the Muslims to fast on three days of every month and on the day of Ashura, and then Allah made fasting obligatory. The obligation was transferred from the fast of Ashura to the fast of Ramadan.
When Allah commanded Muslims to fast the month of Ramadan, the fasting of Ashura became optional.
It is reported that the Prophet (peace be upon him) intended to fast on the ninth and tenth of Muharram. Ibn Abbas reported, “The Messenger of Allah fasted on the day of Ashura and ordered the people to fast on it. The people said, ‘O Messenger of Allah, it is a day that the Jews and Christians honor.’ The Prophet said, ‘When the following year comes, Allah willing, we shall fast on the ninth (and tenth).’ The death of the Prophet came before the following year.” (Sahih Muslim and Abu Dawud)
The practice of fasting on Ashura was known even in the pre-Islamic days, before the Prophet’s mission. It was reported that A’ishah (wife of the prophet) said, “The people of Jahiliyyah used to fast on that day.”
In Sahih Al-Bukhari and other authentic collections of Hadith, it was reported that the Prophet (peace be upon him) and his companions used to fast on the 10th day of Muharram while they were in Makkah, even before migration.
Neither the Prophet (peace be upon him) nor his successors made Ashura a day of mourning or a day of celebration.
Fasting on the day of Ashura is a way to follow the tradition of Prophet Muhammad (peace be upon him) and to expiate our sins of the past year.