n Shia Islam, Arba’in marks forty days after Ashura, which is the death anniversary of Husayn ibn Ali, grandson of the Islamic prophet Muhammad and the third Shia imam. Husayn was killed, alongside most of his relatives and his small retinue, in the Battle of Karbala on Muharram 61 AH (680 CE) against the army of the Umayyad caliph Yazid ibn Mu’awiya (r. 680–683). The battle followed Husayn’s refusal to pledge his allegiance to Yazid, who is often portrayed by Muslim historians as impious and immoral.