From Ibn `Abbas who said: When Allah commanded his Messenger, blessings of Allah on him and his family, to endorse `Ali, and he said to him what he he said to him, he said: "O my Lord, my people were until recently in a state of ignorance (jahiliyya)". Then he proceeded with his Hajj and when he was returning he dismounted at Ghadir Khumm and Allah, the Exalted, revealed to him the verse:
O Messenger, deliver what has been sent down to you from your Lord..’ (5:67).
So he took hold of `Ali’s arm and went out to the people and said: O people, am I not more worthy of authority over you than yourselves?" They said: "Yes indeed, O Messenger of Allah."
He said: "O Allah, of whomsoever I am master, `Ali is his master. O Allah, befriend the one who befriends him, be at enmity with the one who is hostile to him, help the one who helps him, forsake one who forsakes him, aid the one who aids him, love the one who loves him and hate the one who hates him."
Ibn `Abbas said: By Allah, it became an incumbent duty on the people.
Hassan b. Thabit said:
"On the day of al-Ghadir their Prophet calls to them at Khumm; listen to the Messenger calling;
He says: Who is your master and your guardian? They said, not displaying blindness there:
Your God is our Master and you are our guardian, and you will not find from us anyone disobedient concerning the Wilaya.
He said to him: Rise, O `Ali, for I approve of you as Imam and guide after me."