The Umayyads had the practice of cursing Ali during their sermons. Many of the party of Ali did not like that.
One of these men was Hujr ibn Adi, a companion and commander in Ali's army. When he heard the Umayyads cursing Ali, he would shout at them and to make them stop.
But Ziyad ibn Abihi, the governor of Kufah and Basra, would not tolerate such defiance. He decided to find Hujr and make an example of him for others
This episode chronicles the story of Hujr ibn Adi and one of the early incidents that led to the split between Sunnis and Shiites.