Jerusalem: The Biography

* Muhammad’s successors used the title Commander of the Believers. Later the Heads of State were known as Khalifat Rasul Allah – Successor to the Messenger of God – or caliph. Abu Bakr may have used this title but there is no evidence it was again used for another seventy years, until the reign of Abd al-Malik. Then it was applied retrospectively: the first four rulers became known as the Righteous Caliphs.