The Event of Ghadir (Arabic: واقعة الغدير), according to Shia beliefs, is among the most important events in the history of Islam, in which on his return from Hajjat al-Wida', the Holy Prophet (S) introduced Imam Ali (A.S) as his vicegerent and people's guardian after himself at a place called Ghadir Khum, where everyone including greatest Companions pledged their allegiance with Imam Ali (A.S).
Eid al-Adha, also called the "Sacrifice Feast", is one of the Muslim holidays celebrated worldwide each year. It honors the willingness of Ibrahim (Abraham) to sacrifice his son, as an act of submission to God's command. Before he sacrificed his son, God intervened by sending his angel Jibra'il (Gabriel), who then put a sheep in his son's place.
Ali al-Hadi is the tenth of the Twelve Imams after his father Muhammad al-Jawad and before his son Hasan al-Askari.
The event of Ghadir Khumm took place in February 632. It was where, the Islamic prophet Muhammad reportedly announced that "to whomsoever I am Mawla, Ali is also their Mawla." Shia Muslims believe this to be the appointment of Ali as Muhammad's successor.