The festival commemorates the pivotal event at Ghadir Khumm when, by divine command, Prophet Muhammad (peace be upon him and his family) designated Hazrat Ali as the first in the continuing line of hereditary Imams.
Eid-e Ghadir, also known as Eid al-Ghadir Khumm, is an anniversary of special significance to all Shia Muslims. It commemorates the occasion at Ghadir Khumm when, by divine command, Prophet Muhammad (peace be upon him and his family) designated his cousin Hazrat Ali – husband of his daughter and only surviving child, Hazrat Bibi Fatima – as the first in the continuing line of hereditary Imams. The occasion of Ghadir Khumm is also associated with the well-attested Prophetic tradition that he was leaving behind two weighty things: the Holy Qur'an and his progeny, which the Shi'a consider to be the Prophet's testamentary declaration.
Numerous reliable hadith sources – both Shia and Sunni – record the event at Ghadir Khumm. They agree that the Holy Prophet, on his return journey from the final pilgrimage, stopped at an oasis between Mecca and Medina known as Ghadir Khumm, and addressed the large gathering of Muslims who were accompanying him. The Prophet asked them if he had a greater claim upon them than they had upon themselves, to which the Muslims responded affirmatively. The Prophet then went on to say: “He whose Mawla I am, Ali is his Mawla… Oh Allah, help whoever helps him, oppose whoever opposes him, support whoever supports him, forsake whoever forsakes him, and may the truth follow him wheresoever he turns.”
The Shia Ismaili tradition bears witness to the continuity of the authority vested at Ghadir Khumm. The hereditary Imamat has continued over 1 400 years, from Hazrat Ali to the present Imam-of-the-Time, Mawlana Shah Karim al-Hussaini Aga Khan, who is the 49th hereditary Imam and direct descendant of Prophet Muhammad through Hazrat Ali and Hazrat Bibi Fatima.
In commemorating Eid-e Ghadir, the Jamat celebrates the seminal event of Ghadir Khumm, also reaffirming their allegiance to the Imam-of-the-Time as the direct lineal successor and inheritor of the authority of Hazrat Ali.