In the Islamic calendar, the twentieth of Safar, known as In the Islamic calendar, the twentieth of Safar, known as Arba’in , marks forty days after Ashura, the tenth of Muharram. In turn, Ashura is the death anniversary of Husayn ibn Ali, grandson of the Islamic prophet Muhammad and the third Shia imam. Husayn, along with most of his male relatives and his small retinue, were killed on 10 Muharram 61 AH in the Battle of Karbala against the army of the Umayyad caliph Yazid ibn Mu’awiya , having been surrounded for some days and deprived of the drinking water of the nearby Euphrates river.