The Muharram is celebrated during the first month of the Islamic calendar, which is considered the most sacred month of the year. The Shia Muslims consider this month as the month of sorrow and mourning, because the Battle of Karbala was fought during this time.
The 10th day of Muharram is known as the Asurah. Husayun Ibn Ali, the grandson of Prophet Mohammed, and his family was murdered in the Battle of Karbala in AD 680. The Sunni Muslims not only fast on this sanctified day, but carries it till the ninth and tenth or the tenth and eleventh day. Their fast continues till the evening.
Since the Muharram falls on the first month of the year, therefore it is a time for happiness. But the Shias think that it is "haram" to express happiness during this time. The word Muharram is actually derived from the word Haram, which actually means forbidden. The Shias also do not fast as they think that it is a sign of happiness. But only on the tenth day, which is known as the Asurah, the Shias observe voluntary fasting.
The famous quoted lines of Prophet Mohammed from the Fiqh-us-Sunnah, Volume 3, number 25, says, that the prayer during midnight is the best after the obligatory (five daily) prayers. The book also says that the voluntary fasting during the month of Muharram is the best fast.
Muharram also means respect. The Quran was considered the final word after the death of Prophet Mohammed. Since the prophet did not announce any successor, therefore after much dispute, Ali Bakr, a good follower of the Prophet was considered the successor.
But his reign, faced deluge of protest from the mass and he and his family was executed. Since he was murdered on the tenth day of the month of Muharram, it was and is still now considered as the day of sorrow and pain. Actually these circumstances divided the Muslim society into the Shias and the Sunnis. The Shias believe that Ali, Hassan and Hussain are the rightful successors of the Prophet and mourn their death during Muharram.
The first ten days are observed with sadness. The women forbid all adornments and scenes of the battle of Karbala are carried in Shia Mosque. As soon as the moon appears, people recite plaintive verses over sweetened cold drinks, which signify that Hussain and his family had to suffer terrible thirst. During the nine days, paper replica of the martyr's tomb is made. On the tenth day, decorated taziyas and tombs adorned in precious stones are led through the city streets. People also torture themselves by whip lashing their bodies with chains and walking on burning coal.
The popular belief is that if the a few rituals are properly followed on the day of Ashurah, then it leads to great rewards. The rituals are to give alms to the poor, to cut the nails, to recite Surah Ikhlas about 1000 times, to observe fast on this particular day, to be in the company of religious Ulema and many more.
In Islamic history the day is considered to be an auspicious day, as it is believed that Allah created heaven and earth and that on this day he gives his infinite blessings to all. But, inspite of these auspicious days, the Muharram is considered as a month of moaning, as Hussain and his family was murdered.