Muharram is the first month with which the Muslims Ummah begins their lunar Hijrah calendar. Hijrah in Islam, stated with the migration of Prophet Muhammad from Makkah to Madinah. It opened another chapter in the history of Islam.
The month of Muharram is one of the four sanctified months. The Holy Qur'an says
"The number of the months according to Allah is twelve months (mentioned) in the book of Allah on the day which He created heavens and the earth. Among these (twelve months) there are sanctified"
According to the authentic traditions, these four months are Thul Qidah, Thul Hajj, Muharram and Rajab. Rasul in his sermon on the occasion of his last Hajj, has declared, 'One year consist of twelve months, of which four are sanctified months, three of them are in sequence, Thul Qidah, Thul Hajj, Muharram and the fourth is Rajab.
The specific mention of these four months does not mean that any other month has no sanctity, because the month of Ramadan is admittedly the most sanctified month in the year. But these four months were specifically termed as sanctified months for the simple reason that their sanctity was accepted even by the pagans of Makkah.
In fact, every month, out of the twelve, is originally equal to the other. Thus, the sanctity of these four months was recognizes right from the time of Prophet Ibrahim.
Since the pagans of Makkah attributed themselves to prophet Ibrahim they observed the sanctity of these four months and despite the frequent tribal battles, they held it unlawful to fight in these months. Prophet Muhammad (S.A.W) Said "The best fasts after the fast of Ramadan are those of the month of Muharram" The tenth (10th) day of Muharram is the most sacred among all its days. The day is named 'Ashurah'. The Holy prophet, when migrated to Madinah, found that the Jews of Madinah used to fast on the 10th day of Muharram. They said that it was the day on which prophet Musah and his followers crossed the Red Sea miraculously and the Pharaoh was drowned in its water. On hearing this from the Jews, the noble Prophet said "We are more closely related to Musa than you" and directed the Muslims to fast on the day of Ashurah.
Adamu Muhammad Usman, Kafin-Hausa, Jigawa state