Original: The first Caliph to be called Amir al-Mu ` minin was Umar ibn al-Khatt b , the second of the Four Rightly Guided Caliphs ; Uthman ibn Affan and Ali ibn Abi Talib also were called by the same title .
Simplified: It has also been adopted by various Caliphs of the succeeding Umayyad and Abbasid dynasties , as well as by some contemporary Arab monarchs .