Muharram is a blessed month, as mentioned in Sura Tawbah ayah number 36
It is the first month of the Islamic year.
“Verily, the number of months with Allah is twelve months (in a year), so was it ordained by Allah on the Day when He created the heavens and the earth; of them four are Sacred, (i.e. the 1st, the 7th, the 11th and the 12th months of the Islamic calendar). That is the right religion, so wrong not yourselves therein” [Soorat at-Tawbah 9:36].
Fasting on the day of Ashurah (tenth of the month)
Fasting the day of ‘Ashoora’ does expiate for the past year, because the Prophet (peace and blessings of Allaah be upon him) said: “Fasting the day of ‘Arafah I hope Allaah will expiate thereby for the year before it and the year after it, and fasting the day of ‘Ashoora’ I hope Allaah will expiate thereby for the year that came before it.” Narrated by Muslim, 1162.
Which day to fast on Ashurah?
Friday and Saturday (9th and 10th, or August 28 and August 29) or 10th and 11th (August 29 and August 30).
What happened on the day of Ashurah?
It was the day on which the Holy Prophet Musa, peace be upon him, and his followers crossed the Red Sea miraculously and the Pharaoh was drowned in its waters.
Some other people attribute the sanctity of Ashurah to the martyrdom of Sayyidina Hussayn, may Allah be pleased with him, during his battle with the Syrian army. No doubt, the martyrdom of Sayyidina Hussayn is one of the most tragic episodes of our history. Yet, the sanctity of Ashurah cannot be ascribed to this event for the simple reason that the sanctity of Ashurah was established during the days of the Holy Prophet, peace be upon him, much earlier than the birth of Sayyidina Hussayn.
And Allah knows best.