Alī ibn Abī Ṭālib (Arabic: علي بن أﺑﻲ طالب, Transliteration: ʿAlī ibn Abī Ṭālib, [ʕaliː ibn ʔæbiː t̪ˤɑːlib]; 13^thRajab, 24 BH–21^stRamaḍān, 40 AH; approximately October 23, 598 or 600 or March 17, 599 – January 27, 661). The son of Abu Talib, Ali was also the cousin and son-in-law of Islamic prophet Muhammad, ruling over the Islamic Caliphate from 656 to 661, and was the first male convert to Islam.Sunnis consider Ali the fourth and final of the Rashidun (rightly guided Caliphs), while Shias regard Ali as the first Imam and consider him and his descendants the rightful successors to Muhammad, all of which are members of the Ahl al-Bayt, the household of Muhammad. This disagreement split the Ummah (Muslim community) into the Sunni and Shia branches.

Muslim sources, especially Shia ones, state that since Muhammad's time, Ali was the only person born in the Kaaba sanctuary in Mecca, the holiest place in Islam. His father was Abu Talib and his mother was Fatima bint Asad, but he was raised in the household of Muhammad, who himself was raised by Abu Talib, Muhammad's uncle, and Ali's father. When Muhammad reported receiving a divine revelation, Ali was the first male to accept his message, dedicating his life to the cause of Islam.

Shia Islam (Arabic: شيعة‎, Shīʿah) is the second largest denomination of Islam. Adherents of Shia Islam are called Shi'as, Shi'ites, or Shias. "Shia" is the short form of the historic phrase Shīʻatu ʻAlī (شيعة علي), meaning "followers of Ali", "faction of Ali", or "party of Ali".

Like other schools of thought in Islam, Shia Islam is based on the teachings of the Quran and the message of the Islamic prophet Muhammad. In contrast to other schools of thought, the Shia believe that only God has the right to choose a representative to safeguard Islam, the Quran and sharia (based upon verses in the Quran which stipulate this according to the Shia). For this reason, the Shias look to Ali, whom they consider divinely appointed, as the rightful successor to Muhammad, and the first imam. The Shia believe that there are numerous narrations where Muhammad selected Ali as his successor.

Shias believe that Muhammad's family, the Ahl al-Bayt ("the People of the House"), and certain individuals among his descendants, who are known as Imams, have special spiritual and political authority over the community. Therefore, Shias prefer hadith attributed to the Ahl al-Bayt and close associates, and have their own separate collection of hadiths. All Shias agree on the succession of Hassan and Hussein after Ali, but they may differ after Hussein. Hassan and Hussein are described by Shias as "leaders of all youths in Paradise", and believe that these sons of Ali were the true leaders and caliphs of the Muslims. Shias regard Ali as the successor of Muhammad not only ruling over the community in justice, but also interpreting Islamic practices and its esoteric meaning. Hence he was regarded as being free from error and sin (infallible), and appointed by God by divine decree (nass) to be the first Imam. Ali is known as "perfect man" (al-insan al-kamil) similar to Muhammad, according to Shia viewpoint.

Abu Bakr (Abdullah ibn Abi Quhafa) (Arabic: عبد الله بن أبي قحافة, Transliteration: ʿAbd Allāh ibn Abī Quḥāfah, c. 573 CE - 634 CE) also known as Abū Bakr as-Șiddīq (Arabic: أبو بكر الصديق) was a senior companion (Sahabi) and the father-in-law of the Islamic prophet Muhammad. He ruled over the Rashidun Caliphate from 632–634 CE when he became the first Muslim Caliph following Muhammad's death. As Caliph, Abu Bakr succeeded to the political and administrative functions previously exercised by Muhammad, since the religious function and authority of prophethood ended with Muhammad's death according to Islam. He was called Al-Siddiq (The Truthful) and was known by that title among later generations of Muslims.

As a young man, Abu Bakr became a cloth merchant and he traveled extensively in Arabia and neighboring lands in the Middle East, through which he gained both wealth and experience. He eventually came to be recognized as the chief of his clan. On his return from a business trip to Yemen, he was informed that in his absence Muhammad had openly declared his prophethood. Not long after, Abu Bakr accepted Islam and was the first person outside the family of Muhammad to openly become a Muslim. He was instrumental in the conversion of many people to the Islamic faith and early in 623, Abu Bakr's daughter Aisha was married to Muhammad, strengthening the ties between the two men.