"You [Ali] are my brother in this world and the next." (Hadith)
After Uthman's martyrdom, the office of the caliphate remained unfilled for two or three days. Many people insisted that Ali should take up the office, but he was embarrassed by the fact that the people who pressed him hardest were the rebels, and he therefore declined at first. When the notable Companions of the Prophet (peace be on him) urged him, however, he finally agreed.
Ali bin Abi Talib was the first cousin of the Prophet (peace be on him). More than that, he had grown up in the Prophet's own household, later married his youngest daughter, Fatima, and remained in closest association with him for nearly thirty years.
Ali was ten years old when the Divine Message came to Muhammad (peace be on him). One night he saw the Prophet and his wife Khadijah bowing and prostrating. He asked the Prophet about the meaning of their actions. The Prophet told him that they were praying to God Most High and that Ali too should accept Islam. Ali said that he would first like to ask his father about it. He spent a sleepless night, and in the morning he went to the Prophet and said, "When God created me He did not consult my father, so why should I consult my father in order to serve God?" and he accepted the truth of Muhammad's message.
When the Divine command came, "And warn thy nearest relatives" [26:214], Muhammad (peace be on him) invited his relatives for a meal. After it was finished, he addressed them and asked, "Who will join me in the cause of God?" There was utter silence for a while, and then Ali stood up. "I am the youngest of all present here," he said, "My eyes trouble me because they are sore and my legs are thin and weak, but I shall join you and help you in whatever way I can." The assembly broke up in derisive laughter. But during the difficult wars in Mecca, Ali stood by these words and faced all the hardships to which the Muslims were subjected. He slept in the bed of the Prophet when the Quraish planned to murder Muhammad. It was he to whom the Prophet entrusted, when he left Mecca, the valuables which had been given to him for safekeeping, to be returned to their owners.
Apart from the expedition of Tabuk, Ali fought in all the early battles of Islam with great distinction, particularly in the expedition of Khaybar. It is said that in the Battle of Uhud he received more than sixteen wounds.
The Prophet (peace be on him) loved Ali dearly and called him by many fond names. Once the Prophet found him sleeping in the dust. He brushed off Ali's clothes and said fondly, "Wake up, Abu Turab (Father of Dust)." The Prophet also gave him the title of 'Asadullah' ('Lion of God').
Ali's humility, austerity, piety, deep knowledge of the Qur'an and his sagacity gave him great distinction among the Prophet's Companions. Abu Bakr, 'Umar and Uthman consulted him frequently during their caliphates. Many times 'Umar had made him his vice-regent at Medina when he was away. Ali was also a great scholar of Arabic literature and pioneered in the field of grammar and rhetoric. His speeches, sermons and letters served for generations afterward as models of literary expression. Many of his wise and epigrammatic sayings have been preserved. Ali thus had a rich and versatile personality. In spite of these attainments he remained a modest and humble man. Once during his caliphate when he was going about the marketplace, a man stood up in respect and followed him. "Do not do it," said Ali. "Such manners are a temptation for a ruler and a disgrace for the ruled."
Ali and his household lived extremely simple and austere lives. Sometimes they even went hungry themselves because of Ali's great generosity, and none who asked for help was ever turned away from his door. His plain, austere style of living did not change even when he was ruler over a vast domain.
As mentioned previously, Ali accepted the caliphate very reluctantly. Uthman's murder and the events surrounding it were a symptom, and also became a cause, of civil strife on a large scale. Ali felt that the tragic situation was mainly due to inept governors. He therefore dismissed all the governors who had been appointed by Uthman and appointed new ones. All the governors excepting Muawiya, the governor of Syria, submitted to his orders. Muawiya declined to obey until Uthman's blood was avenged. The Prophet's widow Aisha also took the position that Ali should first bring the murderers to trial. Due to the chaotic conditions during the last days of Uthman it was very difficult to establish the identity of the murderers, and Ali refused to punish anyone whose guilt was not lawfully proved. Thus a battle between the army of Ali and the supporters of Aisha took place. Aisha later realized her error of judgment and never forgave herself for it.
The situation in Hijaz (thc part of Arabia in which Mecca and Medina are located) became so troubled that Ali moved his capital to Iraq. Muawiya now openly rebelled against Ali and a fierce battle was fought between their armies. This battle was inconclusive, and Ali had to accept the de facto government of Muawiya in Syria.
However, even though the era of Ali's caliphate was marred by civil strife, he nevertheless introduced a number of reforms, particularly in the levying and collecting of revenues.
It was the fortieth year of Hijra. A fanatical group called Kharijites, consisting of people who had broken away from Ali due to his compromise with Muawiya, claimed that neither Ali, the Caliph, nor Muawiya, the ruler of Syria, nor Amr bin al-Aas, the ruler of Egypt, were worthy of rule. In fact, they went so far as to say that the true caliphate came to an end with 'Umar and that Muslims should live without any ruler over them except God. They vowed to kill all three rulers, and assassins were dispatched in three directions.
The assassins who were deputed to kill Muawiya and Amr did not succeed and were captured and executed, but Ibn-e-Muljim, the assassin who was commissioned to kill Ali, accomplished his task. One morning when Ali was absorbed in prayer in a mosque, Ibn-e-Muljim stabbed him with a poisoned sword. On the 20th of Ramadan, 40 A.H., died the last of the Rightly Guided Caliphs of Islam. May God Most High be pleased with them and grant to them His eternal reward.
With the death of Ali, the first and most notable phase in the history of Muslim peoples came to an end. All through this period it had been the Book of God and the practices of His Messenger - that is, the Qur'an and the Sunnah - which had guided the leaders and the led, set the standards of their moral conduct and inspired their actions. It was the time when the ruler and the ruled, the rich and the poor, the powerful and the weak, were uniformly subject to the Divine Law. It was an epoch of freedom and equality, of God-consciousness and humility, of social justice which recognized no privileges, and of an impartial law which accepted no pressure groups or vested interests.
After Ali, Muawiya assumed the caliphate and thereafter the caliphate became hereditary, passing from one king to another.