Ahl al-bayt in the context of "Shia Islam"

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.

Hasan ibn Ali (Arabic: الحسن ابن علي, romanized: al-Ḥasan ibn ʿAlī; c. 625 – 2 April 670) was an Alid political and religious leader. The eldest son of Ali and Fatima and a grandson of the Islamic prophet Muhammad, Hasan briefly ruled as caliph from January 661 until August 661. He is considered as the second Imam in Shia Islam, succeeding Ali and preceding his brother Husayn. As a grandson of the prophet, he is part of the ahl al-bayt and the ahl al-kisa, and also participated in the event of the mubahala.

During the caliphate of Ali (r. 656–661), Hasan accompanied him in the military campaigns of the First Fitna. Following Ali's assassination in January 661, Hasan was acknowledged caliph in Kufa. His sovereignty was not recognized by Mu'awiya ibn Abi Sufyan (r. 661–680), the governor of Syria, who led an army into Kufa while pressing Hasan for abdication in letters. In response, Hasan sent a vanguard under Ubayd Allah ibn al-Abbas to block Mu'awiya's advance until he arrived with the main army. Meanwhile, Hasan was severely wounded in an abortive assassination attempt by the Kharijites, a faction opposed to both Ali and Mu'awiya. This attack demoralised Hasan's army and led to widespread desertion. Ubayd Allah and most of his troops also defected after Mu'awiya bribed him. In August 661, Hasan signed a peace treaty with Mu'awiya on the condition that the latter should rule in compliance with the Quran and the Sunnah, a council should appoint his successor, and Hasan's supporters would receive amnesty. Hasan retired from politics and abdicated in Medina where he died either from illness or poisoning, though the early sources are nearly unanimous that he was poisoned. Mu'awiya is commonly viewed as the instigator in the murder of Hasan, which removed an obstacle to the succession of his son Yazid I (r. 680–683).