The day of Ashura falls on the tenth day of the month of al-Muharram and has a special significance for Muslims. On the day of Ashura, important events occurred related to the prophets and messengers of Allah. Nuh's (Noah's) ark sailed to land, and Nuh, peace be upon him, fasted every year on this day as a token of gratitude. Also on the day of Ashura was the salvation of Musa (Moses) and his people from the evil pharaoh, who died in the flood along with his army. Musa, peace be upon him, also adopted the custom of fasting every year on this day to express his gratitude to Allah for salvation.

In two Sahihs from Ibn Abbas (r.a.) it is reported that he was asked about the day of Ashura. And he replied: “I have not seen such a day among other days in which the Messenger of Allah (peace and blessings of Allah be upon him) so sought to acquire his dignity, like this day (i.e. the day of Ashura) and this month (i.e. Ramadan) ".

In two “Sahihs” from Mu’awiya (r.a.) it is transmitted: “I heard the Messenger of Allah, peace and blessings of Allah be upon him, say: “This is the day of Ashura, Allah did not oblige fasting (on this day), but I will fast. And whoever wishes, let him fast; whoever does not wish, let him break his fast.” So, fasting on the Day of Ashura is a sunnah of the Messenger of Allah ﷺ.

Muslim cites in his "Sahih" from Abu Qatada that a man asked the Prophet (peace and blessings of Allaah be upon him) about fasting on the day of Ashura, he replied: “(Fasting on this day) serves as an expiation (sins) of the past year.”

There are three options for fasting:

1. Three consecutive days: 9th, 10th, 11th of the month of Muharram.

2. Two consecutive days: 9th and 10th or 10th and 11th of the month of Muharram.

3. One day: 10th day of the month of Muharram.