Tasu'a is followed by Ashura, tenth of Muharram, which marks the death of Husayn ibn Ali, a grandson of the Islamic prophet Muhammad and the third Shia imam.

[1][2] Tasu'a is followed by Ashura, tenth of Muharram, which marks the death of Husayn ibn Ali, grandson of the Islamic prophet Muhammad and the third Shia imam.

[3] Husayn was killed, alongside most of his male relatives and his small retinue, 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.

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

[25] There is a report by the Shia historian Ibn Tawus (d. 1266) that Abbas was killed on Tasu'a in a failed sally to bring water for the thirsty camp.

majlis) is the narration of the stories of Karbala (rawza-khwani, qiraya),[28][14][29] and the recitation of rhythmic elegies and dirges (nawha, niyaha, marsia-khwani),[30][31] all intended to raise the sympathy of audience and move them to tears.

[31] Rooted in ancient Arab practices,[35][36] mild forms of self-flagellation, striking one's face and chest in grief (latm, sina-zani, matam),[31][30][37] are common today in Shia communities.

[38] But there are also extreme forms of self-flagellation (tatbir, tiq-zani, qama-zani), in which the participants strike themselves, usually on the forehead or back, with knives, swords, or chains to which razor blades are attached.

[30] Another mourning ritual is the dramatic reenactment of Karbala narratives (ta'ziya, shabih-khwani), practiced today in Iran, in the western Gulf shore, and in Lebanon.

[31][45] For instance, in Najaf, Iraq, mourners march in the evening of Tasu'a toward the shrine of Ali ibn Abi Talib, the first Shia imam, while carrying decorative torches.