The Prophetic traditions which indicate that Ali should be followed
The prophetic traditions which persuaded me to follow Imam Ali were those I have read in the Sihahs of the Sunnis and were approved by the Shiites, and they have many more. But as usual I only referred to the prophetic traditions that have been agreed on by both parties, and here are some of them:
A. The Prophetic tradition: "I am the city of Knowledge and Ali is its gate."
This tradition  alone should be sufficient to indicate the example that has to he followed after the Messenger of Allah (saw) because the educated man ought to be followed.
Allah - the Most High - said:
Say: "Are those who know and those who do not know alike?"
[Holy Quran 39:9]
He also said:
"Is He then Who guides to the truth more worthy to be followed, or he who himself does not go aright unless he is guided? What then is the matter with you; how do you judge?" [Holy Quran 10:35]
History has recorded many facts telling us that Ali was the most knowledgeable man among all the Companions and they used to consult him on every important matter, and we do not know of any event in which he declined to give his advice.
Abu Bakr said, "May Allah never put me in a predicament that Abu al-Hasan cannot solve. " And Umar said, "If it was not for Ali, Umar would have perished." 
And Ibn Abbas said, "My knowledge and the knowledge of the Companions of Muhammad(saw) is but a drop in seven seas if compared with Ali's knowledge."
And this is what Imam Ali said about himself, "Ask me before you lose me. By Allah, if you ask me about anything that could happen up to the Day of Judgement, I will tell you about it. Ask me about the Book of Allah, because by Allah there is no [Qur'anic] verse that I do not know whether it was revealed during the night or the day, or whether it was revealed on a plain or on a mountain." 
Abu Bakr was once asked about the meaning of the word "Abb" [herbage] in the words of Allah, the Most High:
"And fruits and herbage, A provision for you and for your cattle" [Holy Quran 80:31-32]
Abu Bakr replied, "Which sky would give me shade, and which land would carry me if I say something I do not know about the Book of Allah." And this is Umar saying. "All people are more knowledgeable than I am, even women." He was once asked about the meaning of a Qur'anic verse, and his reaction was to rebuke the man and beat him until he bled, then he said, "Do not ask about matters which may appear bad to you." 
Also he was asked about "al-Kalalah" but he did not know what it meant.
In his "commentary", al-Tabari stated that Umar once said the following, "My knowledge of al-Kalalah is more valuable to me than owning a palace similar to those in Syria."
In one of his books, Ibn Maja quoted Umar as saying "There are three things, if they were explained by the Messenger of Allah, I would have loved them more dearly than anything in the world: Al-Kalalah, usury and the caliphate." God forbid that the Messenger of Allah stayed silent on these subjects!
B. The Prophetic tradition: O Ali! You hold in relation to me the same position as Haroon held in relation to Moses, except that there shall be no prophet after me.
This tradition, as should be apparent to every sensible person, shows the special quality of the Commander of the Believers, Ali, which made him the right person to be the supporter, the guardian and the deputy [or successor] of the Messenger of Allah as Haroon was the supporter, guardian and deputy of Moses when he went to meet his God. There is also the position of Ali vis-a-vis the Prophet which is absolutely equal to the relation between Haroon and Moses, except for the prophethood, which was excluded in the same tradition.
Furthermore, we find in the tradition the fact that Imam Ali was the best Companion, who only came second after the Messenger of Allah (saw).
C. The Prophetic tradition: Ali is the master of all those of whom I am master. O Allah! Love him who loves him and hate him who hates him, help him who helps him, forsake him who forsakes him, and turn justice with him wherever he turns.
This tradition alone is sufficient to reply to the allegations concerning the seniority of Abu Bakr, Umar and Uthman to Ali, who was appointed by the Messenger of Allah as the guardian after him of all the faithful. It is of no consequence for whoever tried to interpret the saying as the friend or the support in order to divert it from its original meaning so that the integrity of the Companions may be kept intact. The Messenger of Allah stood up in the terrible heat addressing the people, saying, "Do you witness that I have a prior right to and superior authority over all the faithful?" They replied, "Yes, O Messenger of Allah. " Thereupon he said, "Ali is the master of all those whom I am a master. . . etc." This is a clear text indicating that the Messenger of Allah had appointed Ali as his successor to lead the nation [of Islam], and the fair and sensible person could not but accept this interpretation and refuse that of the others, thus preserving the integrity of the Messenger of Allah before preserving the integrity of the Companions. Those who give an alternative interpretation to the saying are in fact ridiculing the wisdom of the Messenger of Allah, who gathered the multitude of people, in that unbearable heat, to tell them that Ali was the friend and supporter of the faithful. And what do those, who misinterpret the text in order to preserve the integrity of their masters, say about the procession of congratulation that the Messenger of Allah organised for Ali? It started with the wives of the Messenger, the mothers of the faithful, then Abu Bakr and Umar came and said to him, "Well done Ibn Abi Talib, Overnight you became the guardian [master] of all the faithful."
In fact all the historical evidence gives clear indications that those who misinterpret the above tradition are liars. Woe to those who wrote what they wrote, and woe to them for what they are writing. Allah - the Most High - said. "...a party of them most surely conceal the truth while they know it" [Holy Qur'an 2:146].
D. The Prophetic tradition: Ali is from me and I am from Ali and no one can discharge my duty except myself or Ali.
This honourable tradition  is another clear indication that Imam Ali was only one whom the Messenger authorized to discharge his duties. The Messenger said it on the day of the great pilgrimage when he sent Ali 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 Ali, "O Ali! You will show them the right path when there will be dissension among them after me."  If nobody could discharge the Messenger of Allah's duty except Ali, 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 Ali? 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 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].
E. The Prophetic tradition of the House on the day of Warning.
The Prophet of Allah (saw) said, indicating Ali. This is my brother, my trustee and my deputy [caliph] after me, so listen to him and obey him." 
This is yet another correct tradition cited by many historians at the beginning of the prophetic mission, and considered as one of the Prophet's miracles. However, political intrigues distorted the facts. Then there is no wonder that the oppression which took place then is coming back again in our lifetime. For example, Muhammad Husayn Haykal reproduced the saying in its entirety in his book "The Life of Muhammad", (Page 104, First Edition 1334 Hijri). From the Second Edition onward, the part of the tradition where the Prophet says, "He is my trustee, my deputy [caliph] after me" has been removed.
Also, in al-Tabari's commentary [Tafsir], Volume 19. Page 121, when the Prophet says "My trustee and my deputy [caliph]" was changed to "This is my brother etc. etc", but they failed to recognize that al-Tabari had cited the tradition in its entirety in his Annals Volume 2, Page 319. Look how they change the words and distort the facts ... they want to put out the light of Allah with their mouths, but Allah is spreading His light.
During my investigation I wanted to see the truth, so I searched for the first edition of "The Life of Muhammad". and after some hard work - praise be to Allah - found it, although it cost me considerably. The important thing is that I looked at the distortion and became convinced that the evil people are trying the best they can do to remove the facts. because there is strong evidence in the hands of their "enemies".
When the fair investigator comes across such a blatant distortion, he will no doubt begin to keep away from them and become convinced that they have no evidence except lies and distorted facts. They hire writers to whom they give money, titles and false university degrees in order to write for them books and articles through which they insult the Shiites and accuse them of blasphemy, while at the same time they defend the position, even if it is unjust, of some of the Companions who turned on their heels and exchanged right for wrong after the departure of the Messenger of Allah.
Allah says: "Even thus said those before them, the like of what they say; their hearts are all alike. Indeed We have made the verses clear for a people who are sure." [Holy Quran 2:118]