Sheikh Nâyif al-Hamad, presiding judge at Rimâh District Court
The day of `Ashûrâ' is the 10th day of the month of Muhrram. To observe a fast on the day of `Ashûrâ’ is an emphatic Sunnah (sunnah mu’akkadah). It is not obligatory to fast on this day.
The Prophet (peace be upon him) said: “`Ashûrâ’ is but one of Allah’s days, so whoever wishes to fast on this day should do so, and whoever wishes to refrain from fasting may do so.” [Sahîh Muslim (1136)]
Abû Qatâdah relates that the Prophet (peace be upon him) said: “I hope from Allah that observing the fast of `Ashûrâ’ will expiate for the sins of the past year.” [Sahîh Muslim (1163)]
These hadîth shows us that fasting on the day of `Ashûrâ' by itself is both a valid and a virtuous act.
It is also Sunnah to fast the day before `Ashûrâ’ or the day after it. The Prophet (peace be upon him) said: “Fast the day of `Ashûrâ’, but do so differently than the Jews by fasting the day before it or the day after it.” [Musnad Ahmad (1/241) and Sahîh Ibn Khuzaymah (2095)]
Ibn al-Qayyim writes in Zâd al-Ma`âd (2/75):
There are three ways to observe this fast. The best is to fast the day before `Ashûrâ’ and the day after it. Next in excellence is to fast on the ninth of Muharram as well as the tenth. This is what most of the hadîth indicate. The next is to fast the tenth day by itself.
And Allah knows best.
Source: Islam Today