c.626 - 680
Husayn ibn Ali ibn Ab Talib was the grandson of Muhammad. His mother was Muhammad's daughter Fatima Zahra and his father was Muhammad's cousin, and is the first Imam to Shia Muslims, and the fourth Caliph to Sunni Muslims, Ali ibn Abi Talib. Husayn ibn Ali is revered as the third Imam (Supreme Authority) by Shi'a Muslims.
Husayn was killed in the Battle of Karbala in 680. The anniversary of his death is called Ashura and it is a day of mourning and religious observance for Shi'a Muslims.
This day is well-known because of mourning for the martyrdom of Husayn ibn Ali the grandson of Muhammad, along with 72 members of his family and close friends at the Battle of Karbala .
Yazid I Ibn Muwa'via Ibn Abu Sufyan was in power then and wanted the Bay'ah (allegiance) of Husayn ibn Ali. Yazid was openly going against the teachings of Islam in public and changing the sunnah of Muhammad. Historians agree that if Husayn ibn Ali had not taken the stance that he did, the religion of Islam would not be what it is today.