At-Tabarani mentioned (from Salman) in al-Kabeer that the Prophet (s) had said...

At-Tabarani mentioned (from Salman) in al-Kabeer that the Prophet (s) had said: My guardian, the keeper of my secrets, the best one whom I leave after me, the one, who executes my promises and pays my debts, is Ali bin Abu Talib. And the Prophet (s) might have distinguished some of those, who had diseases in their hearts such as Burayda, with his special saying about Imam Ali (s).

Muhammad bin Hameed ar-Razi mentioned from Burayda that the Prophet (s) had said: Every prophet has had a guardian and heir. My guardian and heir is Ali bin Abu Talib.

And like Anass bin Malik who narrated, as mentioned in Hilyatul Awliya by Abu Naeem, that the Prophet (s) had said to him: O Anass, the first one, who will come to you from this door, is the imam of the pious, the master of the Muslims, the guarder of the religion, the last of the guardians and the leader of the bright-faced people of Paradise. Anass said: Then Ali came and the Prophet (s) got up delightfully and embraced him.

The Prophet (s) said to him: You carry out my affairs instead of me, convey to the people my orders and explain to them what they disagree on after me.[2] [1] Refer to al-Murajaat, murajaa no.36. [2] Al-Murajaat, murajaa no.68.

Anass also narrated that he had heard the Prophet (s) saying: I and Ali are proofs before the umma on the day of resurrection.[1] The Prophet (s) had also entrusted some virtuous women with such traditions like his wife Umm Salama, his uncles wife umm al-Fadhl, Asma bint Umays, Umm Sulaym al-Ansariya and their likes. He had also declared this matter (Alis right in leading the umma) from above his minbar.

He had revealed it to some of his companions in al-Baqee and hinted at it on the day of brotherhood in Mecca before the hijra and the other time in Medina on the day of brotherhood between the Muhajireen and the Ansar. In both occasions the Prophet (s) had taken Imam Ali (s) as his brother preferring him to the all other Muslims saying to him: You are to me as Aaron was to Moses but there will be no prophet after me.