The tenth day of Muharram is the Day of Ashura, which to Shia Muslims is part of the Mourning of Muharram. Sunni Muslims fast during this day, because it is recorded in the hadith that Musa (Moses) and his people obtained a victory over the Egyptian Pharaoh on the 10th day of Muharram; accordingly Muhammad asked Muslims to fast on this day that is Ashura and on a day before that is 9th (called Tasu’a).