Al-Harith was a son of the prominent pre-Islamic Qurayshite Hisham ibn al-Mughira of the Banu Makhzum clan in Mecca. Al-Harith's brother was Abu Jahl, the leader of Meccan opposition to the Islamic prophet Muhammad until his death at the Battle of Badr in 624. Al-Harith also fought against the Muslims at Badr and again at the Battle of Uhud near Medina in 627. Al-Harith embraced Islam during Muhammad's conquest of Mecca in 629/30. Afterward, he fought in the Muslim army against the Arab polytheists at the Battle of Hunayn in 630 and was given a share of the war spoils from that engagement.