When is the day of 'Aashooraa? It is the tenth day of the Islamic Month Muharram. What is so important about it? The Prophet and the Companions used to fast this day. The month of Muharram is from amongst the blessed months and the holy months in Islaam. The Prophet said: The best fasting after Ramadaan is the month of Allaah Muharram, and the best prayer after the obligatory prayer is prayer at night. And in particular the day of 'Aashooraa. Since the Messenger of Allah reached Madeenah he saw the jews fasting this day of 'Aashooraa and upon enquiring they informed him that this day was the day Allah saved His Messenger Moosa and destroyed Fir'awn and his army. Whereupon the Messenger of Allah replied that verily we have more right to Moosa then you and thus the fasting of 'Aashooraa was made obligatory in the early stages in Islaam. Later on when the fasting of Ramadan was made compulsory the fasting of 'Aashooraa was made a Sunnah Mu-akkadah. Shaykh ibn 'Uthaymeen says in his explanation of Riyaadh-as-Saaliheen regarding how to fast: The Prophet orderd the fasting of 'Aashoora but orded us to go against the Jews at the same time. This is why he orded the fasting of the ninth day with the tenth or the eleventh day with the tenth and not the tenth day alone [like the jews used to do] And the best thing to do is to fast ninth and tenth of Muharram. Virtues of  'Aashooraa. The Messenger of Allah 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.  Ibn 'Abbas said that the fasting of Ramadan can be made up for any other day, but when will one who missed this blessed day make up for 'Aashooraa? He also said this is the day when the Prophet Aadam was sent down to earth and the day when Allah accepted his repentance. As a last word, and this is of great importance. There have been many innovations added to this blessed month and blessed day in particular and it is upon every muslim to stay away from any kinds of innovations with regards to the religion since this is considered a lie against Allah and His Messenger.