‘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. 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).
“Muhammad said: ‘He of whom I am the Mawla, Ali is his Mawla. O God, be the friend of him who is his friend and be the enemy of his enemy.’
“This became the proof text for the Shia claim that Ali, the Prophet’s cousin and son-in-law, was the Prophet’s rightful successor after the Prophet’s death in 632. The meaning of Mawla here probably implies the role of patron, lord or protector.” – History in Quotations by M. J. Cohen and John Major.
“…As you know, the Shi’a divided from the Sunni after the death of the Prophet Muhammad. Hazrat Ali, the cousin and son-in-law of the Prophet, was, in Shi’a belief, named by the Prophet to be the Legitimate Authority for the interpretation of the faith. For the Shi’a today, all over the world, he is regarded as the first Imam.” – His Highness the Aga Khan, Tutzing Evangelical Academy, May 20, 2006. 
“In accordance with Shia doctrine, tradition, and interpretation of history, the Holy Prophet (s.a.s.) designated and appointed his cousin and son-in-law Hazrat Mawlana Ali Amiru-l-Mu’minin (a.s), to be the first Imam to continue the Ta’wīl and Ta‘līm of Allah’s final message and to guide the murids, and proclaimed that the Imamat should continue by heredity through Hazrat Mawlana Ali (a.s) and his daughter Hazrat Bibi Fatimat-az-Zahra, Khātun-i-Jannat (a.s).” – The Preamble of The Constitution of the Shia Imami Ismaili Muslims. 
“The Ismaili Imamat is a hereditary institution of Muslim leadership, linked to Prophet Muhammad (peace be upon him and his family) by direct lineal descent through Hazrat Ali, his cousin and son in law. The line of Ismaili Imams has continued uninterrupted by hereditary succession from Hazrat Ali through to the present, 49th Imam, His Highness the Aga Khan.” – The Aga Khan Development Network (AKDN) , Brazil and the Ismaili Imamat sign a Protocol. 
“Allah did choose Adam and Noah, the family of Abraham, and the family of Imran above all people – offspring, one of the other, and Allah knows and hears all things.” (Sura 3, Ayats 33-34).
With regard to the above verse, the Ismaili poet Nizar Quhistani explained:
“We search for a union with the family of the Chosen (Prophet Muhammad). We search for the truth of son after son. We are totally obedient to his offspring, one of the other. There is no other thing we can add to this but itself. We endeavour in our faith so that we do not turn out to be faithless.” – Quoted in Ismailis in the Middle Ages by Shafique Virani.
 To read this and other published speeches at the AKDN Website, please click Tolerance Award from the Evangelical Academy of Tutzing and Speech Archives.
 To read background story and complete preamble, please click The Preamble Of “The Constitution of the Shia Imami Ismaili Muslims”.
 See The Ismaili Imamat note in AKDN–Brazil Protocol.