Abu'l-Qasim Muhammad ibn Abi Bakr al-Siddiq was the son of the first caliph Abu Bakr, born during the Farewell Pilgrimage (10/632) near Dhu'l-Hulayfa. Appointed governor of Egypt under Caliph Ali, he was defeated in the conflict against the forces of Mu'awiya and Amr ibn al-As. In Safar 38 AH (July 658), while fleeing Fustat, he was captured and killed by Mu'awiya ibn Hudayj, and his body was reportedly sewn into a donkey's hide and burned. Because his corpse was burned, his grave is disputed: sources report he was buried outside Fustat, while some hold that only his head was later interred at the site now known as the Zimam Mosque. He is a companion-era figure martyred in Egypt whose maqam is visited there. Sources: TDV İslam Ansiklopedisi "Muhammed b. Ebû Bekir"; Ibn al-Athir, al-Kamil fi'l-tarikh; Wikidata (Q1112754).