On 18th Zilhijjah of the year 10 A.H. (10 March 632 CE) ,after completing the last pilgrimage ,the Holy Prophet(pbuh) along with around...
His message, and Allah will protect you from the people; surely Allah will not guide the unbelieving people.
On receiving the above verse, the Holy Prophet stopped at that very place & delivered a speech an extract of which is :-[....It seems the time has approached when I shall be called away (by Allah) and I shall answer that call. I am leaving for you two precious things and if you adhere to them both, you will never go astray after me. They are the Book of Allah and my Progeny, that is my Ahlul Bayt. The two shall never separate from each other until they come to me by the Pool (of Paradise)." Then the Holy Prophet (pbuh) in an attempt to remind Muslims of his own authority over them said: " Do I not have more right over the believers than what they have over themselves? " Muslims answered unanimously " Yes, O' Messenger of God ". This served as a stepping stone for the announcement of his heir and vicegerent. The Holy Prophet(pbuh) held out the hand of Ali(as) and said: " For whoever I am his Leader (mawla), 'Ali is his Leader (mawla)." The Holy Prophet then continued to say: " O' God, love those who love him, and be hostile to those who are hostile to him."] ..
This day is also known as 'Ahad e-Mahood' in the heavens & as 'Meethaq-e-Maakoodh' on the earth