Adopted from the book : "The Faith of Shi'a Islam" by : Allamah Muhammad Ridha al-Muzaffar"
We believe that the Imamate, like the prophethood, must be an appointment from Allah, through His Messenger, or an appointed Imam. From this point of view, the Imamate is the same as the Prophethood.
It is wrong for People to dispute against him whom Allah has sent as a guide and leader for all people, for they cannot elect him. One who is able to bear the responsibilities of the Imam of the people and the guide of mankind can only be recognized and appointed by Allah. We believe that the Prophet declared who was to come after him (his khalifah) and that he appointed his cousin' Ali ibn Abi Talib as the Commander of the Faithful (Amiru al mu'minin), guardian of the revelation and Imam for the people on several occassions. The prophet obliged everyone to take an oath to agree to' Ali succession on the day of Ghadir.4 and he said at that time:
O faithful! for whomsoever I am his master (mawla) and the authority whom he obeys, 'Ali will be his master. O Allah! be friendly towards the friends of' Ali; help those who help him, and hinder those who hinder him, and the Truth always be with him.
The first place in which the Prophet declared the Imamate was when he had gathered his close relatives and kinsfolk and said them:
He ('Ali) is my brother, inheritor (wasi) and vicegerent (khalifah).
You must listen to him and obey him.
At time the Prophet said this, 'Ali had not yet come of age.
The Prophet spoke many times on this matter:
O 'Ali! your place in relation to me is the same as that of Harun in relation to Musa; except that there will be no prophet after me.
Other traditions indicate that 'Ali had guardianship over the people, as do the verses in the Qur'an such as:
Your friend is only Allah and His Messenger, and the believers who perform the prayer and pay the aims while they do ruku' (5;55)
The last part of this verse was revealed about 'Ali who gave his ring to a beggar while doing ruku' in prayer. Naturally we are not able, in a book such as this, to quote all such traditions and verses, and to consider them.
Imam 'Ali publicly declared the Imamate of Hasan and Husayn, and the latter declared the Imamate of his son' Ali Zayn al-'Abidin, and similarly each Imam was appointed by the previous one.
Notes :
4. 18th Dhu'l Hijjah 10. H.