Arbaeen (), Chehellom (, "the fortieth day") is a Shia religious observance that occurs forty days after the Day of Ashura. It commemorates the martyrdom of Al-Husayn ibn Ali, the grandson of Muhammad, who was martyred on the 10th day of the month of Muharram. Imam Hussain ibn Ali and 71 of his companions were martyred by Ubayd Allah ibn Ziyad's army under the governance of Yazid I in the Battle of Karbala in 61 AH (680 CE). Arbaeen or forty days is also the usual length of mourning after the death of a family member or loved one in many Muslim traditions. Arbaeen is the largest annual pilgrimage in the world, in which millions of people go to the city of Karbala in Iraq. Background According to tradition, the Arbaʽeen pilgrimage has been observed since the year 61 AH of the Islamic calendar (10 October 680) after the Battle of Karbala or the following year. According to tradition, the first such gathering took place when Jabir ibn Abd Allah, a sahabah and the first Arba'ein pilgrim, made a pilgrimage to the burial site of Husayn. He was accompanied by Atiyya ibn Sa'd because of his infirmity and probable blindness. According to tradition, his visit coincided with that of the surviving female members of Muhammad's family and Husayn's son and heir, Imam Ali ibn Husayn Zayn al-Abidin (also spelled Zain-ul-Abideen), who had all been held captive in Damascus by Yazid I, the Umayyad Caliph. Zayn al-Abidin had survived the Battle of Karbala and led a secluded life in deep worship. He lived under pressure and tight surveillance set by Umayyad Caliphate. According to legend, for twenty years whenever water was placed before him, he would weep. One day a servant said to him, 'O son of Allah's Messenger! Is it not time for your sorrow to come to an end?’ He replied, 'Woe upon you! Jacob the prophet had twelve sons, and Allah made one of them disappear. His eyes turned white from constant weeping, his head turned grey out of sorrow, and his back became bent in gloom, though his son was alive in this world. But I watched while my father, my brother, my uncle, and seventeen members of my family were slaughtered all around me. How should my sorrow come to an end?’ Arbaʽeen's performance has been banned in some periods, the last of which was when