text: All officers appointed by this ruler were required to make five promises, among them that they not eat sifted flour or ride Turkic horses.
full_question: All officers appointed by this ruler were required to make five promises, among them that they not eat sifted flour or ride Turkic horses. After his armies surrounded a city in Aelia, this ruler delivered a namesake "assurance" to Patriarch Sophronius. He set up an institution for administration of taxes called the Bayt al-mal, and negotiated a probably-apocryphal treaty listing the rights of dhimmis in Christian Syria, known as his namesake "pact." He died after being stabbed in the navel by the slave Piruz Nahavandi, and introduced the practice of performing the adhan. One of his generals won the Battle of Yarmouk over emperor Heraclius; that general is Khalid ibn al-Walid. His army also defeated Yazdegerd III in the process of conquering Sassanid Persia at the Battle of al-Qadisiyyah. For 10 points, name this predecessor of Uthman and the successor of Abu Bakr, who was the second rightly guided caliph of the Rashidun.
first_sentence: All officers appointed by this ruler were required to make five promises, among them that they not eat sifted flour or ride Turkic horses.
raw_answer: Umar ibn al-Khattab [or Omar]