Umar ibn Sa'ad
‘Umar ibn Sa‘ad (Arabic: عمر بن سعد) (fl. 620–686) was a son of Muhammad's companion, Sa'ad ibn Abi Waqqas. He was born in Madinah and later moved to Kufa, which was built by his father and stayed there until his death.
He took orders from Ibn Ziyad. He was one of the leaders of the troops who killed Husayn ibn Ali in the Battle of Karbala in 680, the first major battle of the Second Islamic Civil War (Second Fitna).