The succession to Muhammad raises questions about the leadership of Islam after his death: Muhammed's successor, how they should be elected, conditions of legitimacy and the role of successor. Answers to these questions have led to several divisions in the Muslim community since the first century of Muslim history, giving rise to the Sunni, Shia and Khawarij schools. After Muhammad's death in AD 632, disagreement broke out over who should succeed him as leader of the Muslim community. Since none of his sons survived into adulthood, hereditary succession was not an option. Umar (Umar ibn al-Khattab), a prominent companion of Muhammad, nominated Abu Bakr. Others added their support, and Abu Bakr was made the first caliph. This choice was disputed by some of Muhammad's companions, who believed that Ali (Ali ibn Abi Talib), his cousin and son-in-law, had been designated his successor.[1] During the First and Second Fitnas the Islamic community divided into a number of groups, each of which had a specific idea about successorship. After the Rashiduncaliphate evolved into monarchies and sultanates, Sunnis held power in most areas; Shias emerged in opposition.

Sunnis believe that although Muhammad did not appoint a successor, Abu Bakr was elected the first caliph by the Muslim community and they recognize the first four caliphs as Muhammad's successors. Shias believe that Muhammad named his successor, Ali, at Ghadir Khumm; Muslim leadership belonged to the person determined by divine order.[2][3] The two groups also disagree on Ali's attitude towards Abu Bakr and the two caliphs who succeeded him: Umar and Uthman ibn Affan. Sunnis and the Zaydis emphasize Ali's acceptance and support of their rule; according to the Twelver Shia, he distanced himself from them and was prevented from fulfilling the religious duty that Muhammad had given him. They maintain that if Ali was the rightful successor (as ordained by God), it would have been his duty as leader of the Muslim nation to make war with Abu Bakr, Umar and Uthman; however, he had neither the military strength nor the willingness to wage civil war amongst the Muslims.[4] Ali believed that he could fulfil his imamate without fighting.[5]

Qasim ibn Muhammad ibn Abu Bakr's mother was from Ali's family; Qasim's daughter, Farwah bint al-Qasim, was married to Muhammad al-Baqir and was the mother of Jafar al-Sadiq. Qasim ibn Muhammad ibn Abu Bakr was the grandson of Abu Bakr, the first caliph, and the grandfather of Jafar al-Sadiq. The Zaydis (the largest Shia group before the Safavid Dynasty and currently the second-largest group) believe that Zayd ibn Ali (the uncle of Jafar al-Sadiq) was betrayed by the people in Kufa, who told him: "May God have mercy on you! What do you have to say on the matter of Abu Bakr and Umar ibn al-Khattab?" Zayd ibn Ali said, "I have not heard anyone in my family renouncing them both nor saying anything but good about them ... when they were entrusted with government they behaved justly with the people and acted according to the Qur'an and the Sunnah"[7][8]

Most of Islamic history was transmitted orally until after the rise of the Abbasid Caliphate.[9] Historical works of later Muslim writers include the traditional Muslim biographies of Muhammad and quotes attributed to him (the sira and hadith literature), which provide further information on Muhammad's life.[10] The earliest surviving written sira (biographies and quotes attributed to Muhammad) is Sirah Rasul Allah(Life of God's Messenger) by Ibn Ishaq (d. 761 or 767 AD).[11] Although the original work is lost, portions survive in the recensions of Ibn Hisham (d. 833) and Al-Tabari (d. 923).[12] Many (but not all) scholars accept the accuracy of these biographies, although this accuracy is uncertain.[13] Studies by J. Schacht and Ignác Goldziher have led scholars to distinguish between legal and historical traditions. According to William Montgomery Watt, although legal traditions could have been invented, historical material may have been primarily subject to "tendential shaping" rather than invented.[14] Modern Western scholars are much less likely than Sunni Islamic scholars to trust the work of the Abbasid historians, and Western historians approach the classic Islamic histories with varying degrees of circumspection.

Hadith compilations are records of the traditions (or sayings) of Muhammad—his biography, perpetuated by community memory for it guidance. The development of hadith is a crucial element of the first three centuries of Islamic history.[15] Early Western scholars mistrusted the later narrations and reports, regarding them as fabrications. Leone Caetani considered the attribution of historical reports to `Abd Allah ibn `Abbas and Aisha as primarily fictitious, preferring accounts reported without isnad by early historians such as Ibn Ishaq. Wilferd Madelung has rejected the indiscriminate dismissal of everything not included in "early sources", instead judging later narrative in the context of history and compatibility with events and figures.[16]

After Muhammad united the Arabian tribes into a single Muslim religious polity during the final years of his life, his death in 632 was followed by disagreement over who would succeed him as leader of the Muslim community.[18] At a small gathering attended in Saqifah a companion of Muhammad, Abu Bakr, was nominated to lead the community. Others supported him, and Abu Bakr became the first caliph. This choice was disputed by other companions of Muhammad, who believed that Muhammad had chosen Ali as his successor.[3][19] However Sunnis allege that Ali accepted the subsequent leadership of Abu Bakr, Omar and Uthman.[20]

According to Wilferd Madelung, after Abu Bakr's election he and a few other companions went to Fatimah's house to receive homage from Ali and his supporters gathered there. When Umar threatened to set the house ablaze unless they came out, Zubayr came out with his sword drawn. He lost his sword, and Umar's men carried him off. Evidence exists that Fatimah's house was searched, and Ali reportedly said that if he had been forty men he would have resisted. Abu Bakr isolated the Banu Hashim (who, according to Al-Zuhri, refused to swear allegiance) for six months.[21] According to Lesley Hazleton, Umar decided to break into Fatima's house instead of burning it and flung himself at the door.[22] Twelver Shi'ite sources relate that Umar set fire to Fatimah's door before kicking it open, crushing Fatimah (who was trying to hold the door shut). The blow killed Mohsin, Fatimah's unborn son, broke her ribs and later caused her death). This is disputed by Sunni Muslims, who believe that no such conflict ever occurred. Twelvers believe that Ali, under orders from Muhammad not to fight back, was put in chains; when Abu Bakr's selection to the caliphate was a fait accompli, Ali withheld his allegiance until after Fatimah's death because he did not want to cause strife in the nascent Muslim community.[23] He buried Fatimah at night, with none of Abu Bakr's supporters present, and the location of her grave is uncertain.

Twelvers believe that Ali was convinced of the legitimacy of his claim to the caliphate based on his close kinship with Muhammad and his knowledge of, and service to, Islam; he told Abu Bakr that his delay in pledging allegiance (bay'ah) was based on his belief in his own title. Ali did not change his mind when he pledged allegiance to Abu Bakr, Umar and Uthman; he did so for the unity of Islam when the Muslims had clearly turned away from him.[3][24]

Sunni Muslims relate a number of hadith (oral traditions) in which Muhammad recommended shura (consultation) as the best method for reaching community decisions. According to this view, he did not nominate a successor because he expected that the community would choose a new leader (the custom in Arabia at the time). Some Sunnis believe that Muhammad had indicated his reliance upon Abu Bakr as second-in-command, calling on him to lead prayers and make rulings in Muhammad's absence. A narrative by Mousa Ibn 'Aoqbah in Al-Dhahabi's book, Siyar a`lam al-nubala (Arabic: سير أعلام النبلاء‎‎), reads: " ... Then Ali and Al-Zobair said, 'We see that Abu Bakr is worthier to be the rightful successor of the prophet than anyone else ... '"[25]

According to a musnad (supported) hadith, Muhammad made a speech at Ghadir Khumm in which he said, "Of whomsoever I am the mawla, Ali is his mawla".[citation needed]Mawla has a number of meanings in Arabic. Although Shi'ites translate it as "master" or "ruler" and believe that Muhammad did not make 120,000 people wait in the desert for three days only to tell them to support Ali, some Sunni scholars say that Muhammad was saying that his friends should befriend Ali; it was a response to Yemeni soldiers who had complained about Ali.[26] A similar incident is described in Ibn Ishaq's Sirah, in which Muhammad reportedly said: "Do not blame Ali, for he is too scrupulous in the things of God, or the way of God, to be blamed."(Guillaume p. 650)[full citation needed] Sunnis believe that interpreting an expression of friendship and support as the appointment of a successor is incorrect, and the leadership dispute after Muhammad's death proved that his statement was not an appointment.

Others believe that Muhammad meant "master" in his use of mawla to describe Ali at Ghadir Khumm but it was a description of Ali's spiritual superiority among the Muslims, not a decision about succession. These Sunnis also reject the translation of mawla as "friend". The word is discussed in Patronate and Patronage in Early and Classical Islam, edited by Monique Bernards and John Nawas:

Mawla may refer to a client, a patron, an agnate (brother, son, father's brother, father' brothers son), an affined kinsman, (brother-in-law, son-in-law), a friend, a supporter, a follower, a drinking companion, a partner, a newly-converted Muslim attached to a Muslim and last but not least an ally. Most of these categories have legal implications ... Mawla is commonly translated as "a client".[27]

Muhammad asked permission from his other wives to spend his last days with Aisha. Sunnis believe that before he died, Muhammad indicated his faith in Abu Bakr by asking him to lead the prayers in the mosque (a highly-visible role undertaken, when possible, by Muhammad himself). Historically, the imam is the leader of his Muslim community.[28]

The ansar (helpers of Muhammad and the muhajirun) held a meeting to discuss choosing a new leader of their part of the community. When news of the meeting spread, Abu Bakr, Umar and Abu Ubaidah ibn al-Jarrah rushed to the scene. Abu Bakr argued that if the ansar chose a leader of themselves only, the Muslim community would split; the new leader must come from the Quraysh (Muhammad's tribe), and Sa'd ibn Ubadah agreed. Abu Bakr suggested that the people should choose Umar or Abu Ubayda, since both were capable. Umar took Abu Bakr's hand and declared his allegiance (bay'ah, an Arabian custom), followed by the rest of the gathering. However, this decision would not have been binding on the rest of the Muslims unless they gave their bay'ah (which all did, except Ali's supporters).

Sunni Muslims consider Ali one of Muhammad's prominent companions of the ten, including Abu Bakr, Umar and Uthman, who were promised the gift of paradise. They consider him a righteous caliph and accept his hadiths.

Twelvers believe that since a prophet is appointed by God, only God can appoint his successor. Some cite Quranic verses such as 38:26[29] and 2:124[30] in which Allah assigned his successor on earth. Shia believe that Moses did not ask his people to conduct a shura and assign his successor; Allah selected Aron to succeed Moses for his 40-night absence. Shia scholars refer to hadiths such as the Hadith of the pond of Khumm, Hadith of Position and Hadith of the Twelve Successors to prove that God, through Muhammad, chose Ali as successor. When the chief of Banu Amir asked Muhammad for a share of leadership in return for defeating Muhammad's enemy, Muhammad replied: "That is for God to decide; He will entrust leadership to whomever He will"; community leadership was not decided by the people.[31]

Ali, Muhammad's cousin and a leader in battle, was often entrusted with command and was left in charge of the community in Medina when Muhammad led the Battle of Tabouk. Ali was also the husband of Muhammad's daughter, Fatimah, and the father of his grandchildren Hasan and Husayn. Ali's father was Abu Talib ibn Abd al-Muttalib, Muhammad's uncle, foster father and protector. As a member of Abu Talib's family, Muhammad was like an older brother and guardian to Ali (who, as a youth, was among the first to accept Islam). A charismatic defender of the faith, Ali was assumed by some to claim a leadership position after Muhammad's death. In the end, however, Abu Bakr assumed control of the Muslim community.

Shia believe that a number of ahadith indicate that Muhammad left specific instructions about his successor. Some of these ahadith have names, such as the pond of Khumm, Safinah, Thaqalayn, Haqq, position and warning. There are different versions of these ahadith, and the following two are the most relevant to the Shia argument for Ali.

In 632 AD, Muhammad made his last pilgrimage to the Kaaba in Mecca. Some early accounts say that when he returned to Medina, he and his followers stopped at a spring and landmark known as Ghadir Khumm. Muhammad delivered a speech to his assembled followers in which he reportedly said, "For whoever I am his mawla, Ali is his mawla".[citation needed]Mawla (friend) occurs a number of times in the hadith,[36] including: "... وَقَالَ لِزَيْدٍ " أَنْتَ أَخُونَا وَمَوْلاَنَا" (Muhammad said to Zaid, "You are our brother (in faith) and our freed slave [mawla]".[37]

In this mutawatir hadith, Muhammad said: "Verily, I am leaving with you two precious things, the Book of God and my progeny, my ahl al-bayt; for as long as you cling to these two, you will never go astray; and truly they will not be parted from each other until they join me at al-Kawthar".[38]

Muhammad founded Islam when he was forty years old, and kept his mission secret for its first three years. He was ordered to begin the open declaration of his message when God told him, "Warn your nearest relations".[39] Muhammad organized a feast, known as Da‘wat dhul-‘Ashīra (Summoning the Family). He invited about forty men from the Banu Hashim, and asked Ali to make arrangements for the dinner. When Muhammad wanted to speak to the gathering about Islam, Abu Lahab ibn 'Abdul Muttalib said: "Your host has long since bewitched you". The guests left before Muhammad could present his message to them, but he invited them again the following day. After the feast, he said to them:

O Sons of ‘Abdul-Muttalib! By Allāh, I do not know of any person among the Arabs who has come to his people with better than what I have brought to you. I have brought to you the good of this world and the next, and I have been commanded by the Lord to call you unto Him. Therefore, who amongst you will support me in this matter so that he may be my brother (akhhī), my successor (wasiyyī) and my caliph (khalifatī) among you?[40]

This was the first time that Muhammad publicly asked his relatives to accept him as the messenger and prophet of God, and the first time he asked someone to help him. Ali, the youngest, was the only one who stood up and said: "I will be your helper, O Prophet of God."[40] Muhammad then put his hand on the back of Ali's neck and said, Inna hadhã akhhí wa wasiyyí wa khalífatí fíkum, fasma‘û lahu wa atí‘û (Verily, this is my brother, my successor, and my caliph amongst you; therefore, listen to him and obey).[40]

Muhammad compared his ahl al-Bayt to Noah's Ark: "Is not the likeness of my ahl al-bayt among you like the ark of Noah among his folk? Whoever takes refuge therein is saved and whoever opposes it is drowned." As Noah's Ark was the sole salvation of his people, ahl al-Bayt was the only salvation for the people of that time.[38]

Muhammad said, "Just as the stars are a means of securing the people of the earth against drowning, my ahl al-bayt is a means of securing my community from division" (a way to unify the community).[38]

Soon after returning from the Farewell Pilgrimage, Muhammad became ill. He was nursed in the home of his wife Aisha, the daughter of Abu Bakr. The Shia believe that most prominent Muslims, expecting Muhammad's death and a power struggle, disobeyed his orders to join a military expedition bound for Syria. They stayed in Medina, waiting for Muhammad's death and a chance to seize power.

According to Abd Allah ibn Abbas (Muhammad's cousin) in Book 13, Hadith 4016, the dying Muhammad said that he wished to write (or dictate) a letter detailing his wishes for the community. According to ibn Abbas' Sahih Muslim,

Ibn Abbas reported: When Allah's Messenger (may peace be upon him) was about to leave this world, there were persons (around him) in his house, 'Umar b. al-Khattab being one of them. Allah's Apostle (may peace be upon him) said: Come, I may write for you a document; you would not go astray after that. Thereupon Umar said: Verily Allah's Messenger (may peace be upon him) is deeply afflicted with pain. You have the Qur'an with you. The Book of Allah is sufficient for us. Those who were present in the house differed. Some of them said: Bring him (the writing material) so that Allah's Messenger (may peace be upon him) may write a document for you and you would never go astray after him And some among them said what 'Umar had (already) said. When they indulged in nonsense and began to dispute in the presence of Allah's Messenger (may peace be upon him), he said: Get up (and go away) 'Ubaidullah said: Ibn Abbas used to say: There was a heavy loss, indeed a heavy loss, that, due to their dispute and noise. Allah's Messenger (may peace be upon him) could not write (or dictate) the document for them.

When Muhammad died, Umar said that he would return and threatened to behead anyone who accepted his death. When Abu Bakr returned to Medina, he spoke to Umar (who then admitted that Muhammad had died); the Shia believe that this was a ploy on Umar's part to delay the funeral and give Abu Bakr time to return to Medina.

When Muhammad died, his closest relatives (Ali and Fatimah) took charge of his body. While they were washing his body and preparing it for burial (carried out by the family of the deceased in Islam), a meeting—about which Ali and the muhajirun were not informed—was held in the Saqifah and Abu Bakr was chosen as the new leader.

According to Wilferd Madelung, as Ali had refused to pledge allegiance (bay'ah) to Abu Bakr many Medina Muslims of Medina had also refused; they were known as Shī‘at ‘Alī (the party of Ali). Madelung wrote that it took six months to coerce them to submit to Abu Bakr.[43] When he refused to pledge allegiance, Ali's house was surrounded by an armed force led by Abu Bakr and Umar:[44]

In Madinah, Umar took charge of securing the pledge of allegiance of all residents. He dominated the streets with the help first of the Aslam and then the Abd Al-Ashhal of Aws, who in contrast to the majority of Khazraj, quickly became vigorous champions of the new regime. The sources mention the actual use of force only with respect to Companion Al-Zubayr who had been together with some others of the Muhajirun in the house of Fatimah. Supposedly, Umar threatened to set the house on fire unless they came out and swore allegiance to Abu Bakr.[45]

Twelvers believe that Umar pushed his way into Ali's house and Fatimah, who was pregnant, was crushed behind the door. She miscarried her unborn son, whom the Shia mourn as Muhsin ibn Ali, and soon died of her injuries. Ali buried her secretly at night, since he did not want Abu Bakr or Umar (whom he blamed for her death) to attend her funeral, and the Shia blame Abu Bakr and Umar for the deaths of Muhammad's daughter and grandson.[46]

Western historians largely reject the Shi'ite claim that Muhammad appointed Ali as his successor.[48]Wilferd Madelung suggests that the succession of Abu Bakr was problematic (unlike other modern historians), and Ali may indeed have expected to assume leadership at Muhammad's death:[48] According to Madelung,

In the Qur’an, the descendants and close kin of the prophets are their heirs also in respect to kingship (mulk), rule (hukm), wisdom (hikma), the book and the imamate. The Sunnite concept of the true caliphate itself defines it as a succession of the prophet in every respect except his prophethood. Why should Muhammad not be succeeded in it by any of his family like the earlier prophets? If God really wanted to indicate that he should not be succeeded by any of them why did He not let his grandsons and other kin die like his sons? There is thus a good reason to doubt that Muhammad failed to appoint a successor because he realized that the divine design excluded hereditary succession of his family and that he wanted the Muslims to choose their head by Shura. The Qur’an advises the faithful to settle some matters by consultation, but not the succession to prophets. That, according to the Qur’an, is settled by divine election, God usually chooses their successors, whether they become prophets or not from their own kin.[49]

Madelung bases this on the hadith of the pond of Khumm. Ali later insisted that his religious authority was superior to that of Abu Bakr and Umar.[50]