The Day of Ashura is on the 10th day of Muharram in the Islamic calendar and marks the climax of the Mourning of Muharram.
It is commemorated by Shi’a Muslims as a day of mourning for the martyrdom of Husayn ibn Ali, the grandson of Prophet Muhammad at the Battle of Karbala on 10 Muharram in the year 61 Hijri.
According to Sunni Muslim tradition, Ibn Abbas narrates that Muhammad came to Medina and saw the Jews fasting on the tenth day of Muharram. He asked, “What is this?” They said, “This is a good day, this is the day when Allah saved the Children of Israel from their enemy and Musa (Moses) fasted on this day.” So he fasted on this day and told the people to fast.
In some Shi’a regions of Muslim countries such as Afghanistan, Iran, Turkey, Azerbaijan,Iraq, Lebanon, Bahrain, and Pakistan, the Commemoration of Husayn ibn Ali has become a national holiday and most ethnic and religious communities participate in it. Even in predominantly Hindu majority but secular country like India, Ashura (10th day in the month of Muharram) is a public holiday.