ʿĀSHŪRĀʾ is the tenth day of Muḥarram, the first month of the Muslim calendar. Its general significance as a fast day for Muslims derives from the rites of the Jewish Yom Kippur (Day of Atonement). The Arabic term ʿāshūrāʾ is based on the Hebrew word ʿasor with the Aramaic determinative ending.

Scholars are not agreed as to the exact day on which ʿĀshūrāʾ was observed in early Islam. Early ḥadīth tradition seems to indicate that the day possessed special sanctity in Arab society even before Islam. Thus the Jewish rite, which the Prophet observed in Medina in 622 CE, only helped an already established Arab tradition to acquire religious content and hence greater prestige. The Jewish character was soon obscured, however, through its incorporation into the...