Muslim holy day observed on the 10th of Muḥarram, the first month of the Islamic year (Gregorian date variable). ʿĀshūrāʾ was originally designated in AD 622 by Muhammad, soon after the Hijrah (Hegira), as a day of fasting from sunset to sunset, probably patterned on the Jewish Day of Atonement, Yom Kippur. When Jewish-Muslim relations became strained, however, Muhammad made Ramadan (Ramaḍān) the Muslim month of fasting, leaving the ʿĀshūrāʾ fast a voluntary observance, as it has remained among the Sunnites.

Among the Shīʿites, ʿĀshūrāʾ is a major festival, the tazia (taʿziyah), commemorating the death of Ḥusayn, son of ʿAlī and grandson of Muhammad, on the 10th of Muḥarram, AH 61 (October 10, 680), in Karbalāʾ (present-day Iraq). It is a period of expressions of grief and of pilgrimage to Karbalāʾ; passion plays are also presented, commemorating the death of Ḥusayn.