Abu Bakr

Umar ibn al-Khattab (Arabic: عُمَر بْن ٱلْخَطَّاب, romanized: ʿUmar ibn al-Khaṭṭāb; c. 584 – 644), also spelled Omar, was the second Rashidun caliph, ruling from August 634 until his assassination in 644. He succeeded Abu Bakr (r. 632–634) and is regarded as a senior companion and father-in-law of the Islamic prophet Muhammad.

Initially, Umar opposed Muhammad, who was his distant Qurayshite kinsman. However, after converting to Islam in 616, he became the first Muslim to openly pray at the Kaaba. He participated in nearly all of Muhammad’s battles and expeditions, and Muhammad conferred upon him the title al-Fārūq ("the Distinguisher") for his sound judgement. After Muhammad’s death in June 632, Umar pledged allegiance to Abu Bakr as the first caliph and served as his chief adviser. In 634, shortly before his death, Abu Bakr nominated Umar as his successor.

The Rashidun (Arabic: الراشدون, romanized: al-Rāshidūn, lit. 'the rightly-guided') are the first four caliphs (lit. 'successors') who led the Muslim community following the death of Muhammad: Abu Bakr (r. 632–634), Umar (r. 634–644), Uthman (r. 644–656), and Ali (r. 656–661).

The reign of these caliphs, called the Rashidun Caliphate (632–661), is considered in Sunni Islam to have been 'rightly guided' (Arabic: rāshid), meaning that it constitutes a model (Sunnah) to be followed and emulated from a religious point of view.

In Muslim tradition the Quran is the final revelation from God, Islam's divine text, believed to be delivered to the Islamic prophet Muhammad through the angel Jibril (Gabriel). Muhammad's revelations were said to have been recorded orally and in writing, through Muhammad and his followers up until his death in 632 CE. These revelations were then compiled by first caliph Abu Bakr and codified during the reign of the third caliph Uthman (r. 644–656 CE) so that the standard codex edition of the Quran or Muṣḥaf was completed around 650 CE, according to Muslim scholars. This has been critiqued by some western scholarship, suggesting the Quran was canonized at a later date, based on the dating of classical Islamic narratives, i.e. hadiths, which were written 150–200 years after the death of Muhammad, and partly because of the textual variations present in the Sana'a manuscript. Muslim scholars who oppose the views of the Western revisionist theories regarding the historical origins of the Quran have described their theses as "untenable".

More than 60 fragments including more than 2000 folios (4000 pages) are so far known as the textual witnesses (manuscripts) of the Qur'an before 800 CE (within 168 years after the death of Muhammad), according to Corpus Coranicum. However, in 2015, experts from the University of Birmingham discovered a single folio later called the Birmingham Quran manuscript, which is possibly the oldest manuscript of the Quran in the world. Radiocarbon analysis to determine the age of the manuscript revealed that this manuscript could be traced back to some time between 568 and 645 AD. Selected manuscripts from the first four centuries after the death of Muhammad (632–1032 CE) are listed below.

From 613 to 619 CE, the Islamic prophet Muhammad gathered in his hometown of Mecca a small following of those who embraced his message of Islam and thus became Muslims. The first person who professed Islam was his wife, Khadija bint Khuwaylid. The identity of the second male Muslim, after Muhammad himself, is disputed largely along sectarian lines, as Shia and some Sunni sources identify him as the first Shia imam Ali ibn Abi Talib, a child at the time, who grew up in the household of his cousin, Muhammad. Other sources report that the first male convert was Abu Bakr, who later succeeded Muhammad as the first Sunni caliph, or Muhammad's foster son, Zayd ibn Haritha. While it is difficult to establish the chronological order of early conversions, the identities of early Muslims are known with some certainty.

Khalifa or Khalifah (Arabic: خليفة, romanized: Khalīfa; commonly "caliph" in English) is a name or title which means "successor", "ruler" or "leader". It most commonly refers to the leader of a Caliphate, but can also be used as a title among various Islamic religious groups and others. There were four Rashidun caliphs after Muhammad died, beginning with Abu Bakr. The Khilafah (or Caliphate) was then contested and gave rise to the eventual division of the Islamic Umma into two groups, the Sunni and the Shi'a who interpret the word Khalifa in differently nuanced ways.

The earliest Islamic uses include 'Khaleefa(ḥ)' in The Qur'an, 2:30, where God commands the angels to bow down to Adam) with reverence. "Vicegerent", therefore, is more at "divinely-guided spokesman" than "deputy" in this context and leads to the discovery of the role of Imam in Islam, from the Shi'i or Shi'a point of view where, it is claimed, the spiritual Khilaafat or designation of Khaleefa in this meaning of spiritual and temporal guide falls upon the first Imam, 'Ali ibn Abi Talib, (who received his mission from his cousin Muhammed and who also conceded the Khilaafat to the election and claim of the politically more powerful and more popular leader and his senior, Abu Bakr). In the Shi'i tradition, the dissolved claim to the Khilaafat by Shi'i thereafter crystallised into Imamat which continued with his descendants after him through appointment by nass, or designation.

Mu'awiya I (c. 597, 603 or 605–April 680) was the founder and first caliph of the Umayyad Caliphate, ruling from 661 until his death. He became caliph less than thirty years after the death of the Islamic prophet Muhammad and immediately after the four Rashidun ('rightly-guided') caliphs. Unlike his predecessors, who had been close, early companions of Muhammad, Mu'awiya was a relatively late follower of Muhammad.

Mu'awiya and his father Abu Sufyan had opposed Muhammad, their distant Qurayshite kinsman and later Mu'awiya's brother-in-law, until Muhammad captured Mecca in 630. Afterward, Mu'awiya became one of Muhammad's scribes. He was appointed by Caliph Abu Bakr (r. 632–634) as a deputy commander in the conquest of Syria. He moved up the ranks through Umar's caliphate (r. 634–644) until becoming governor of Syria during the reign of his Umayyad kinsman, Caliph Uthman (r. 644–656). He allied with the province's powerful Banu Kalb tribe, developed the defenses of its coastal cities, and directed the war effort against the Byzantine Empire, including the first Muslim naval campaigns. In response to Uthman's assassination in 656, Mu'awiya took up the cause of avenging the murdered caliph and opposed the election of Ali. During the First Muslim Civil War, the two led their armies to a stalemate at the Battle of Siffin in 657, prompting an abortive series of arbitration talks to settle the dispute. Afterward, Mu'awiya gained recognition as caliph by his Syrian supporters and his ally Amr ibn al-As, who conquered Egypt from Ali's governor in 658. Following the assassination of Ali in 661, Mu'awiya compelled Ali's son and successor Hasan to abdicate and Mu'awiya's suzerainty was acknowledged throughout the Caliphate.

Shia Islam is the second-largest branch of Islam. It holds that Muhammad designated Ali ibn Abi Talib (r. 656–661) as both his political successor (caliph) and as the spiritual leader of the Muslim community (imam). However, his right is understood to have been usurped by a number of Muhammad's companions at the meeting of Saqifa, during which they appointed Abu Bakr (r. 632–634) as caliph instead. As such, Sunni Muslims believe Abu Bakr, Umar (r. 634–644), Uthman (r. 644–656) and Ali to be 'rightly-guided caliphs', whereas Shia Muslims regard only Ali as the legitimate successor.

Shia Muslims believe that the imamate continued through Ali's sons, Hasan and Husayn, after which various Shia branches developed and recognized different imams. They revere the ahl al-bayt, the family of Muhammad, maintaining that they possess divine knowledge. Shia holy sites include the shrine of Ali in Najaf, the shrine of Husayn in Karbala, and other mausoleums of the ahl al-bayt. Later events, such as Husayn's martyrdom in the Battle of Karbala (680 CE), further influenced the development of Shia Islam, contributing to the formation of a distinct religious sect with its own rituals and shared collective memory.