Ashura is the 10th day of Muharram (the 1st month of Islamic caledar). The famous practice of the Prophet (SAW) on the day is fasting that is named Ashura fast. This fasting emerged as a result of the fact that when the Prophet came to Medina, he found (the Jews) fasting on the day of 'Ashura' (i.e. 10th of Muharram). The Prophet said, "I am closer to Moses than they." So, he (SAW) observed the fast (on that day) and ordered the Muslims to fast on it. But, he commanded the Muslims to be different from the Jews, who took it as a festival.
The fasting of 'Ashura' is very meritorious in Islam because, the Prophet (SAW) said: "...For fasting the day of 'Ashura', I hope that Allah will accept it as expiation for the year that went before." (Muslim 6/ 2602). This is from the bounty of Allah towards the Muslim, to fast one day and have the sins of a whole year forgiven. But, it should be noted that this expiation is for all minor sins according to Imaam al-Nawawi in al-Majmoo' Sharhal-Muhadhdhab. And Shaykh al-Islam Ibn Taymiyah in al-Fataawa al-Kubra,part 5.
Days to fast: It is mustahabb (encouraged) to fast on the ninth and the tenth of Muharram. Al-Nawawi (RA) said: "Our companions said: 'Ashura' is the tenth day of Muharram and Tasu'a' is the ninth day. This is our opinion, and that of the majority of scholars (al-Majmu'). This is what Ahmad said, and it is the opinion of Ishaaq."
It is reported that when the Messenger of Allah (SAW) fasted on the day of 'Ashura and commanded that it should he observed as a fast, they (his Companions) said to him: Messenger of Allah, it is a day, which the Jews and Christians hold in high esteem. Thereupon the Messenger of Allah (SAW) said: When the next year comes, God willing, we would observe fast on the 9th.
But the Messenger of Allah (SAW) died before the advent of the next year. (Sahih Muslim 6/2528)
These are some of the authentic sayings and compilation of scholars such as Bukhari, Muslim, works of Shaykh Saalih al-Munajjid (Saudi Arabia) etc. concerning the month of Muharram. But, unfortunately after the prophet, a lot of customs and practices which lack authentic proof from shariah have been attached to the month of Muharram in Muslim world. Sadly, this customs and practices do cause many Muslim to violate the sanctity of the month yearly.
Fabricated customs and practices: Some of the fabricated customs and practices in the month of Muharram include the following: Believing that Ashura is a day to openly express grief and that means no shower, no clean clothes, no grooming, and no saying Salam on Ashura etc. Celebrating Ashura with parts of sacrificial animal of 'Eid-il-adha, making a kind of light and all unIslamic celebration including Kayo-kayo festival that was formally attributed with Islam but has now been infiltrated with unIslamic practices such as music by fuji musician, dancing, taking of alcohol etc. all in the name of Kayo-kayo festival.
From the foregoing, a Muslim is expected to keep the sanctity of the month of Muharram by carrying out the dictates of Shariah appropriately and moving away from what is forbidden including fabricated customs and practices that lack authentic proof from shariah.
We ask Allah to make us followers of the Sunnah of His Noble Prophet, to make us live in Islam and die in a state of Mumeen. May He help us to do that which He loves and which pleases Him.