“The religious leadership of the Ismaili Imam goes back to the origins of Shia Islam when the Prophet Muhammad appointed his son-in-law, Ali, to continue his teachings within the Muslim community. The leadership is hereditary, handed down by Ali’s descendants, and the Ismailis are the only Shia Muslims to have a living Imam, namely myself.” 
“The Ismaili Imamat is a supra-national entity, representing the succession of Imams since the time of the Prophet. But let me clarify something more about the history of that role, in both the Sunni and Shia interpretations of the Muslim faith. The Sunni position is that the Prophet nominated no successor, and that spiritual-moral authority belongs to those who are learned in matters of religious law. As a result, there are many Sunni imams in a given time and place. But others believed that the Prophet had designated his cousin and son-in-law, Ali, as his successor. From that early division, a host of further distinctions grew up — but the question of rightful leadership remains central. In time, the Shia were also sub-divided over this question, so that today the Ismailis are the only Shia community who, throughout history, have been led by a living, hereditary Imam in direct descent from the Prophet.
“…As you build your lives, for yourselves and others, you will come to rest upon certain principles. Central to my life has been a verse in the Holy Quran which addresses itself to the whole of humanity. It says: “Oh Mankind, fear your Lord, who created you of a single soul, and from it created its mate, and from the pair of them scattered abroad many men and women…”
“I know of no more beautiful expression about the unity of our human race — born indeed from a single soul.” 
‘Id-e-Ghadir is celebrated by the Shi ‘ite communities to mark the event that took place at Ghadir Khumm (Valley of the Pond) on the 18th Dhul-Hijjah (which falls on September 30 or October 1 in 2015). This event commemorates the designation (appointment by way of nass) of Hazrat All as the ‘Amir-ul-Mu’minin (commander of the faithful) and Imamul-Muslimin’ (the Imam of the community of believers) at Ghadir-i Khumm when the Prophet (s.a.s.) was returning from his Last Pilgrimage (hajjatul-wida) in the year 632 AC. On this occasion, the Prophet publicly proclaimed Ali to be his successor  in guiding the community after the end of the institution of Nubuwwah. According to the Shi’a doctrine, tradition and interpretation of history, the designation of Hazrat Ali marked the beginning of the institution of Imamah. The designated Imam was to continue the ta’wil (interpretation) and talim (teaching) of Allah’s Final Message, i.e. the Holy Qur’an.
Accordingly, throughout the course of the history, the Shi’a have commemorated this occasion as a mark of recognition and acceptance of Allah’s mercy to mankind by bestowing continued guidance. Each Imam, since the time of Hazrat Ali has designated his successor. The Imam in his time has continued to guide his followers according to the prevailing conditions. His function has always been to look after the welfare of the community both in spiritual and worldly (material) matters. His guidance to his followers is that they should lead their lives in such a way so as to practice their Faith with a sense of balance and harmony, ensuring that there is no conflict between the two aspects of an individual’s life. The practice of the Faith thus becomes the way of life.
Presently, the Shi’a Imami Ismaili Muslims celebrate the day of accession of their present Imam to the office of Imamah as Yaum-e Imamat or Imamat Day. This occasion is celebrated as a mark of gratitude to Allah in having bestowed His mercy and bounty in guiding them through the office of the Imam on Sirat al-Mustaqim (the Straight Path).
Date re-posted: September 30, 2015 (The Id-e-Ghadir article had first appeared on this blog in 2013, and has been adapted from Ilm magazine, December 1989).
 Voices: “The Power of Wisdom” – His Highness the Aga Khan’s Interview with Politique Internationale (English translation)
 In a Dynamic and Stirring Address to Members of the Canadian Parliament, His Highness the Aga Khan Shares His Faith Perspectives on the Imamat, Collaboration with Canada, the Muslim World Community (the Ummah), the Nurturing of Civil Society, Early Childhood Education, Voluntary Work, and the Unity of the Human Race
 Vagglieri, Ghadir Khumm, The Encyclopedia of Islam, Vol II, E.J. Brill, 1965, pp. 993-994