Piece of jesus cross.
Omar's successor did not share the same fate. Uthman bin Affan was chosen by an electoral council of six prominent companions to succeed Omar as the third caliph. Although he belonged to one of Mecca's most noble and wealthy clans, Uthman lived a simple and pious life, giving much of his wealth to charity. Although he held great stocks of goats and camels, in his last years he possessed only what he needed for pilgrimage.
Unlike Omar who was strict in enforcing austere standards, Uthman allowed his governors to amass wealth. For example, Mu'awiyah, who was the governor of Syria and a member of the Umayyad clan to which Uthman belonged, accumulated a fortune. Slowly accusations of nepotism and murmurs of discontent began to spread, leading, eventually, to angry mobs surrounding the caliph's house and trapping him inside. Uthman forbade his supporters to draw swords, as Muhammad had once warned that once the sword was drawn between his followers, it would never be sheathed until the Day of Judgment. The rebels stormed his house and slew him during his prayers, leaving the Islamic community irreparably divided.
During the dark period following Uthman's murder, Muhammad's cousin and son-in-law, Ali, ruled as the fourth and last of the "rightly guided" caliphs. Ali had been one of the first to convert to Islam. When Muhammad's kinsmen had rejected Muhammad, it was ten-year-old Ali who answered Muhammad's call. Many believe that Ali was the rightful heir to Muhammad and should have been the first caliph. From the beginning of Ali's rule, he was pressed to avenge Uthman's death, in particular by Muhammad's widow, Aishah. Ali agreed that the murderers should be brought to justice, but he would not risk starting a war when the very existence of the nation and Islamic community was at stake. Instead he wisely moved to replace the old governors, rid his government of corruption, and thereby prevented accusations of corruption.
After Mu'awiyah refused to step down, a series of civil wars erupted, and the unity of the Islamic community was shattered. Ali was murdered by members of an extremist sect that had emerged during this period of civil war.
This period of civil war spawned the two major sects of Islam, the Sunni and Shi'a. The Shi'a believe that only members of the prophet's bloodline should have been caliphs. Of the four "rightly guided caliphs," they revere only Ali. Also, because of his simplicity, piety, and inner spiritual strength, Ali is also regarded as a founder of the Islamic mystic path, Sufism.
After the four "rightly guided caliphs," the Muslim world fell under the rule of Mu'awiyah. The caliphate became hereditary, and the Umayyad dynasty was established. The rulers of the Muslim world began, then, to live like traditional kings. The caliphs focused more on worldly wealth and luxury. The divide between Sunni and Shi'a grew and became a cause of bloodshed, a cause that has continued to the present day. However, the virtues of the first four caliphs survived, and Muslims today turn to these four as models of leadership and as spiritual exemplars.