Guided4

D. The Prophetic tradition: Ali is from me and I am from Ali and no one can discharge my duty except myself or Ali. 

Sunni Documents:

Sunan, Ibn Majah, vol 1 p 44
Khasais, al Nasai, p 20
Sahih, al Tirmidhi, vol 5 p 300
Jami al Usul, Ibn Kathir, vol 9 p 471
al Jami al Saghir, al Suyuti, vol 2 p 56
al Riyadh al Nadirah, Tabari, vol 2p 229 

This honourable tradition is another clear indication that Imam Ali(a.s) was only one whom the Messenger (SBUH&HP) authorized to discharge his duties. The Messenger(Salaam Be Upon Him&His Progeny) said it on the day of the great pilgrimage when he sent Imam Ali(a.s) with Surat Bara'a instead of Abu Bakr, who came crying and asked, "O Messenger of Allah ! Reveal something for me." The Messenger answered, "My Lord ordered me that nobody can discharge my duty except myself or Ali." 

There is another supporting tradition that the Messenger of Allah, said on another occasion in honour of Hazrat Ali(a.s), "O Ali! You will show them the right path when there will be dissension among them after me."

Sunni Documents:

Tarikh, Ibn Askir, vol 2 p 488
Kunuz al Haqa'iq, al Mauawi, p 203
Kanz al Ummal, vol 5 p 33

If nobody could discharge the Messenger of Allah's duty except Hazrat Ali(a.s), and if he was the one who would show them the right path after dissension appeared among them after him; then how could a person who did not know the meaning of "al-Abb" and "Kalalah" be more senior to Imam Ali(a.s)? This is sadly one of the tragedies that have been inflicted on our nation and prevented it from doing the duties that Allah has chosen for it. We could not blame Allah or the Messenger of Allah or the Commander of the Believers Ali ibn Abi Talib(Salaam Be Upon Them) for that, but the blame falls squarely on those who rebelled and changed, and Allah - the most High - said: "And when it is said to them, "Come to what Allah has revealed and to the Messenger. They say, "That on which we found our fathers is sufficient for us. " What! Even though their fathers knew nothing and did not follow the right way" [Holy Qur'an 5:104].