تاريخ الطبري
According to the "History of the Prophets and Kings", after the death of Muhammad, Abu Bakr, Umar and Abu Ubaidah ibn al-Jarrah and the Anṣār of Medina held consultations and selected Abu Bakr as the first caliph. Then 'Abd al-Rahman ibn 'Awf and Uthman, companion and son-in-law of Muhammad and also essential chief of the Banu Umayyah, selected Umar as the second caliph after the death of Abū Bakr and the other Anṣar and Muhajirun accepted him.