Ashura, the tenth day of the month of Muharram. The importance of this day for Shiites is due to the incident of Karbala on the 10th day of Muharram in 61 lunar year. Imam Hussain (a.s.) was martyred on the day of Ashura along with his companions in Karbala in the battle with Kufa army under the command of Umar bin Saad.
