Shia Islam is the second-largest branch of Islam. It holds that the Islamic prophet Muhammad designated Ali ibn Abi Talib as his successor and the Imam after him, most notably at the event of Ghadir Khumm, but was prevented from succeeding Muhammad as the leader of the Muslims as a result of the choice made by some of Muhammad's other companions at Saqifah. This view primarily contrasts with that of Sunni Islam, whose adherents believe that Muhammad did not appoint a successor before his death and consider Abu Bakr, who was appointed caliph by a group of Muhammad's other companions at Saqifah, to be the first rightful (rashidun) caliph after Muhammad.
In Shia Islam, the Imamah is a doctrine which asserts that certain individuals from the lineage of the Islamic prophet Muhammad are to be accepted as leaders and guides of the ummah after the death of Muhammad. Imamah further says that Imams possess divine knowledge and authority (Ismah) as well as being part of the Ahl al-Bayt, the family of Muhammad. These Imams have the role of providing commentary and interpretation of the Quran as well as guidance.
Zaydism is one of the three main branches of Shia Islam that emerged in the eighth century following Zayd ibn Ali‘s unsuccessful rebellion against the Umayyad Caliphate. Zaydism is typically considered to be a branch of Shia Islam that comes closest to the Sunni, although the "classical" form of Zaydism over the centuries had changed its posture with regard to Sunni and Shia traditions multiple times, to the point where interpretation of Zaydi as Shia is often based on just their acceptance of Ali as a rightful successor to prophet Muhammad. Mainstream ("twelver") Shia sometimes consider Zaydism to be a "fifth school" of Sunni Islam. Zaydis regard rationalism as more important than Quranic literalism and in the past were quite tolerant towards Sunni Shafi'ism, a religion of about half of the Yemenis.
The Alids are those who claim descent from Ali ibn Abi Talib, the fourth Rashidun caliph and the first imam in Shia Islam. Ali was also the cousin and son-in-law of the Islamic prophet Muhammad. The main branches are the Hasanids and Husaynids, named after Hasan and Husayn, the eldest sons of Ali from his marriage to Fatima, the daughter of Muhammad. As the progeny of Muhammad, they are revered by all Muslims. The Alids have led various movements in Islam, and a line of twelve Alids are the imams in Twelver Shia, the largest Shia branch.
Ali ibn al-Husayn al-Sajjad, also known as Zayn al-Abidin was the great-grandson of the Islamic prophet Muhammad, and the fourth imam in Shia Islam, succeeding his father, Husayn ibn Ali, his uncle, Hasan ibn Ali, and his grandfather, Ali ibn Abi Talib.
Al-Mukhtar ibn Abi Ubayd al-Thaqafi was a pro-Alid revolutionary based in Kufa, who led a rebellion against the Umayyad Caliphate in 685 and ruled over most of Iraq for eighteen months during the Second Fitna.
Muhammad ibn al-Hanafiyya was a son of Ali ibn Abi Talib, who was the fourth caliph in Sunni Islam and the first imam in Shia Islam. Ibn al-Hanafiyya was an effective lieutenant for his father Ali during his caliphate. After the assassination of Ali and the deaths of his two sons Hasan and Husayn, many recognized Ibn al-Hanafiyya as the head of the House of Ali. Claiming to represent Ibn al-Hanafiyya, Mukhtar al-Thaqafi rose in Iraq in 686 to avenge Husayn and his relatives, who were massacred in 680 CE by forces of the Umayyad caliph Yazid bin Mu'awiya. The quiescent Ibn al-Hanafiyya did not actively associate with this rebellion but was still rescued by Mukhtar when he was detained by the rival caliph Ubayd Allah ibn Ziyad. Support for Ibn al-Hanafiyya continued even after the defeat and death of Mukhtar in 686–687 in the form of the Kaysanites, a now-extinct Shia sect that traced the imamate to Ibn al-Hanafiyya and his descendants, particularly his son Abu Hashim. After the death of Ibn al-Hanafiyya in 700–701, some Kaysanites declared that he was the Mahdi, the eschatological Islamic leader who would reappear in the end of time and eradicate injustice and evil. The Kaysanites later provided the organizational structure for the Abbasids to overthrew the Umayyads in 750–751.
The Mahdi is a figure in Islamic eschatology who is believed to appear at the End of Times to rid the world of evil and injustice. He is said to be a descendant of Muhammad, who will appear shortly before Prophet Isa.
The Kaysanites were a Shi'i sect of Islam that formed from the followers of Al-Mukhtar. They traced Imamate from Muhammad ibn al-Hanafiyyah and his descendants. The name Kaysaniyya was most likely derived from the name of Mukhtar's chief guard, Abu Amra Kaysan.
The Muhammadite Shia were a Shia sect who believed that due to the supposed lack of a son for Hasan al-Askari, they had to rethink the legitimacy of his Imamate. Therefore, they instead believed in the Imamate of his brother Muhammad al Askari ibn Imam Ali al-Hadi, who died 7 years before the death of his father. However, the Muhammadites denied the death of Muhammad al Askari ibn Imam Ali al-Hadi, and claimed that his father had pointed to him and appointed him as the Imam to succeed himself, and had mentioned him by his name and person. These beliefs, falsely according to them, are what were agreed by all.
The Waqifite Shia were a Shia sect who accepted the Imamate of Musa al-Kadhim, but refused to accept the Imamate of his successor Ali ar-Ridha.
The Dukayniyya Shia were a sect of the Zaidi branch of Shia Islam. The Dukayniyya Shia were led by Abu Nu'aym al-Fadl ibn al-Dukayn and Ibrahim ibn al-Hakam.
The Khalafiyya Shia were a subsect of the Zaidi branch of Shia Islam.
The Ghurabiyya Shi‘a were a ghulat sect of Shi‘a Islam. They are one of the best known of a few extremist Shi‘i sects who adopted the belief that the angel Gabriel was mistaken when passing on the prophecy to Muhammad instead of Ali.
The Bazighiyya Shia was a Ghulat sect of Shia Islam. They believed that Ja’far ibn Muhammad al-Sādiq was God. Today, descendants of the followers of the sect either converted to Shia Islam or mainstream Twelver Shia Islam.
The Yaʽfuriyya Shia was a ghulat sect of Shia Islam. The sect was also referred to as the Muʽammariyya Shia. The Yaʽfuriyya believed in reincarnation and a man named Muʽammar al-Kufi to be their Lord.
Shia Islam originated as a response to questions of Islamic religious leadership which became manifest as early as the death of Muhammad in 632 CE. The issues involved not only whom to appoint as the successor to Muhammad, but also what attributes a true successor should have. Sunnis regarded Caliphs as a temporal leaders,. To the Shiite, however, the question of succession is a matter of designation of an individual (Ali) through divine command. In the same way, Shias believed that each Imam designated the next Imam by the leave of God. So within Shia Islam it makes no difference to the Imam's position whether he is chosen as a Caliph or not.
Jarudiyya, also known as Jarudism, is among the first branches of Zaydi Islam, attributed to Abu'l-Jarud Ziyad ibn al-Mundhir. Among the theorists of the Jarudiyya are Fadl ibn Zubayr al-Rasani, Mansur ibn Abi al-Aswad, and Harun ibn Saad al-Ajli. Abu Khalid al-Wasiti is another prominent figure in this school. Jarudiyya beliefs include: Zayd ibn Ali as imam, Ali's preference over other Sahabah and the necessity of rising up against a Tyrant.
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