Hawzah News Agency ­– In the hadiths quoted above, the Holy Prophet clearly indicated who was to be his successor, either in a general or a specific way, such that any one of them would suffice as proof for those who objectively seek after the truth. Nonetheless, in order that his message on this issue reach the ears of all the Muslims, far and wide, and in order to foreclose any possibility of doubt or hesitation on this score, the Prophet halted the great mass of pilgrims returning from the Hajj at a place called Ghadir Khumm, telling his companions that he had received a command from God to deliver a message to them. This divine message pertained to the accomplishment of a momentous obligation, one so great that if
he did not carry this out, the Prophet would not have performed his duty. As the Qur’an says:
 

O Messenger, make known that which hath been revealed to thee from thy Lord, for if thou do it not, thou wilt not have conveyed His Message. God will protect thee from the people. (Sura al-Ma’ida, V: 67)90
 

A pulpit was erected; he stood upon it and then proclaimed: ‘Shortly, I shall be answering labbayk [‘at Thy service’] to my Lord’s call; what will you say of me?’
 

In reply, the people assembled said: ‘We bear witness that you have conveyed unto us the religion of God; you wished only for our well-being, and you exerted yourself to the utmost. May God bestow the best of rewards upon you!’
Then he asked: ‘Do you testify to the Oneness of God, to my message, and the reality of the Day of Resurrection?’
All those present so testified. Then he said: ‘I shall enter the Pool (al-Kawthar) before you; take care how you treat two precious things that I am leaving behind.’
Someone asked what was meant by the ‘two precious things’. The Prophet replied: ‘The one is the Book of God, and the other is my progeny. And God, the Subtle, the Aware, has told me that these two will not be separated until the Day of Judgment, when they shall join me. Do not come too close to these two things, lest you perish; and do not stray too far from them, lest you perish.’

Then he clasped the hand of ‘Ali, raising it aloft, so that all could see the two hands together, and spoke as follows: ‘O people, who has a greater claim over the believers than their own souls?’ They replied: ‘God and His Messenger know best.’ [The Prophet said:] ‘Truly God is my Mawla and I am the mawla of the believers, and I have a greater claim over them than their own souls.’ Then he said three times:

‘For whoever has me as his mawla, ‘Ali is his mawla.’
 

Then he said: ‘My Lord, be the friend of whoever is ‘Ali’s friend, and the enemy of whoever is ‘Ali’s enemy; love whoever loves him and hate whoever hates him; help whoever helps him and abandon whoever abandons him, wherever he may be. Let those who are present convey this to those who are absent.

Reference:

Ayatollah Jafar Sobhani, Doctrines of Shii Islam, A Compendium of Imami Beliefs and Practices, Translated and Edited by Reza Shah-Kazemi, published by I.B.Tauris Publishers, london • new york  2003.