'fortieth') marks forty days after Ashura, which is the martyrdom 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 10 Muharram 61 AH (680 CE) against the army of the Umayyad caliph Yazid ibn Mu'awiya (r. 680–683).

In Shia Islam, Karbala symbolizes the eternal struggle between good and evil, the pinnacle of self-sacrifice, and the ultimate sabotage of Muhammad's prophetic mission.

Pilgrims arrive there in large numbers, often on foot, and many from the city of Najaf, some eighty kilometers away, home to the shrine of Ali ibn Abi Talib, the first Shia imam.

[4] Husayn, alongside most of his male relatives and his small retinue, were killed on 10 Muharram 61 AH (10 October 680 CE) in the Battle of Karbala against the army of the Umayyad caliph Yazid ibn Mu'awiya (r. 680–683), having been surrounded for some days and deprived of the drinking water of the nearby Euphrates river.

[5][6][7] The fight took place in the desert land of Karbala, en route to the nearby Kufa, whose residents had invited Husayn to lead them against Yazid.

[8] In Shia Islam, Karbala symbolizes the eternal struggle between good and evil,[9][10] the pinnacle of self-sacrifice,[11] and the ultimate sabotage of Muhammad's prophetic mission.

[12] Historically, the event served to crystallize the Shia community into a distinct sect and remains an integral part of their religious identity to date.

Upon arrival in Karbala on Arba'in,[27][28] they met Jabir ibn Abd Allah (d. 697), a companion of Muhammad,[22] who had learned about the death of Husayn through a divine sign.

[22] The veracity of Ibn Tawus' account has therefore been questioned by some, including the Shia scholar Husain Noori Tabarsi (d. 1902) and the Islamicist Mahmoud M. Ayoub (d. 2021).