Eid al-Ghadir which is a festive day observed by Shiite Muslims on the 18th of Dhu al-Hijjah in the Islamic calendar is celebrated in Iran.

This day is to celebrate the appointment of Ali ibn Abi Talib by Muslims' Prophet Mohammad (PBUH) as his immediate successor.

It marks the anniversary of Prophet Mohammad (PBUH) sermon, described in Hadith of the pond of Khumm, in which he stated, Whomsoever's master (maula) I am, Ali is also his (maula) master. O' God, love those who love him, and be hostile to those who are hostile to him."

Ghadir tradition is one of the conclusive evidences for the immediate guardianship and caliphate of ‘Ali (a.s.) after the Prophet (s.a.w.a.), and the researchers render a special importance to it.