For Sunnis, the first four successors of Muhammad: Abu Bakr al-Siddiq, Umar ibn al-Khattab, Uthman ibn Affan, and Ali ibn Abi Talib. All were prominent Companions of Muhammad and belonged to the tribe of Quraysh. The period of their rule is considered a golden age, when the caliphs were consciously guided by Muhammad's practices. The period saw the establishment of Arab Muslim rule over the heartlands of the Middle East and preparation for conquests and expansion carried out under subsequent dynasties. Umar is portrayed as the dominant personality among the caliphs, establishing many of the fundamental institutions of the classical Islamic state. Uthman is generally held responsible for the canonization of the Quran as it is known today. He is described as personally pious but lacking the character needed to withstand unscrupulous relatives. Uthman's murder by malcontents opened a period of fitnah (disorder, civil war), which brought about the disintegration of the previously united community, the takeover of the caliphate by the Umayyad family, and the end of the era of Arabia-centered Islam.
See also Abu Bakr al-Siddiq; Ali ibn Abi Talib; Umar ibn al-Khattab; Uthman ibn Affan