In the name of Allah the most Merciful Beneficent
The guidance of Muslim Ummah is a continuous requirement. There can not be an era or age of time when guidance is not required. As the guidance is a constant need, so the availability of a guide who can provide the guidance to the Muslim Ummah is also a continuous indispensable need.
The history is full of anecdotes of nations and communities in the life periods of different prophets (‘a) that these nations were at a point in time well guided but after the death of their prophets (‘a) the nations gradually deviated from the guidance and got totally perverted.
In his life the Holy Prophet (S) was the greatest of all divine guides who provided direct guidance and leadership to the Ummah and led it with utmost and complete success to the triumph of Islam and victory of divine message of Tawheed and establishment of an Islamic state based upon divine laws in which justice and truth were among fundamental ruling principles.
However, after the death of Holy Prophet (S) the question poses itself who will carry forward the torch of divine guidance and provide leadership to the Ummah? Did the Holy Prophet (S) appoint a leader for the Muslims as his successor after him, or was the selection of the leader was left to the Ummah?
In this brief write up we will inshaAllah attempt to discuss these points with respect to the incident of Ghadeer and logical analysis of the question of successorship as done by Shaheed Ayatollah Sayyid Baqir al-Sadr in his work entitled: “A Study on the Question of Al-Wilaya” 
Shaheed al-Sadr has discussed three possibilities in his above mentioned essay. The first possibility being that the Prophet left the Ummah without any successor after him, the second one that he wanted the Muslims to choose their leader for themselves through Saqifa or consultation, and the last one being that the Prophet appointed Imam Ali (‘a) as his successor – the Imam of Ummah.
The Prophet (S) was assuming the leadership of a revolutionary faith, inducing radical transformations of the customs, structures, and concepts of society. The path for such transformation was long and the faith which the Prophet practiced was immaculate. He had to deal with people belonging to the Age of Ignorance and raise them to new institutions, thus converting them into believing men and women who could carry the new light and uproot the twisted tree of ignorance from hearts and minds.
The Prophet (S) made astonishing headway in the task of transformation in a very short time, but it was necessary for this task of transformation to continue on its way even after the death of the Prophet (S). So to believe that Prophet Muhammad (S) adopted a passive approach for leadership after him is to attribute a lack of insight to the Prophet (S).
To think that such a thing could happen is actually a sin – besides, all logic and reason with many evidences refute such an attribution. The Prophet (S) was well aware of the maturity of the faith of the Muslims who had just emerged from the dark alleys of pre-Islam ignorance, and they were certainly not in a condition to cope with the vacuum of leadership.
There were also many hypocrites present in the garb of Muslims, and the Prophet (S) knew it well. He (S) was well aware of the dangers to Islam after him, and hence, claims of any kind of passivity on his part for the future of Islam are not acceptable.
In fact, both Shi’a and Sunni narrators have this tradition recorded in their authentic works that Umar was with a group of men in the house when the Prophet (S), before his death, said: “Bring me parchment and pen so that I may write something for you after which you shall never go astray.”
In fact, this act of the Prophet illustrates clearly that he was deeply concerned about the dangers which had to be faced in the future. It also shows that he recognized the need to plan ahead so as to protect the Ummah from deviation and save it from inattentiveness and disintegration. It is thus totally impossible to substantiate any claim of passivity leveled against the Prophet.
The second possibility is that the Prophet (S) adopted a positive policy concerning the future of the Ummah and Islam, and he advocated the appointment of a Shura or counsel, which would be entitled to select a leader of the Muslims.
Had the Holy Prophet (S) adopted a positive attitude towards Shura after him, he would have found it absolutely necessary to educate the Ummah and the faithful concerning the principles of Shura with its rules and details, while also mentally and spiritually preparing the Islamic society to accept this system. But we can easily discover that the Holy Prophet never sought to educate the Ummah for any such plans for future.
We do not find any narrations attributed to the Prophet (S) giving details of principles, legal aspects or theoretical concepts of Shura. Therefore, we can conclude that Holy Prophet (S) did not advise Shura for the Ummah after his death.
The Shura, which was formed after the Prophet’s (S) death, could not survive for even a short time. The first Caliph neglected it and appointed the second Caliph himself, while the second one formed a six-member group enshrining the right to elect a leader amongst them. In this way, Saqifa collapsed immediately after it was formed. The first Caliph regretted the fact that he was elected too speedily, while the second one regretted the first one’s election saying that it was a slip, and on many occasions he himself confessed his inability in handling the affairs of Ummah.
The third approach is the only possibility, which is consistent with the nature of facts and is logical in light of the circumstances surrounding Islam, Muslims and the Prophet (S). The Holy Prophet (S) adopted a positive stance towards the future of Islam after his death, and as per the orders of Allah he chose Imam Ali (‘a) who had a deep involvement in the formation of Islam. Prophet Muhammad (S) specifically prepared the Imam so that he could exemplify the intellectual authority and political leadership of the experience, and maintain the leadership of the Ummah and its ideological structure after the Holy Prophet’s (S) death.
Imam Ali (‘a) himself described his unique relationship with the Holy Prophet (S): “You know of my connection with the Messenger of Allah, my close kinship to him and my intimate position. He put me on his lap when I was a child, hugged me to his breast, embraced me in his bed, so that his body touched mine and so I smelled his scent, and would also chew things and give them to me to eat. But he did not find me lying in my speech or pompous in my act. I used to follow him as the small camel follows its mother and every day he showed me part of his moral acts and ordered me to do likewise. Every year he used to take me to Hira and only I could see him, for at that period of time of Islam there was only the Messenger of Allah, Khadija and myself as the third, as nobody else lived in the house. So I saw the light of revelation and the message and smelled the fragrance of prophecy.”
There are a great many indications from the lifetime of Imam Ali (‘a) after the death of the Prophet (S) which reveal the Prophet’s private ideological training of Imam Ali (‘a) and reflect the effects and results of this private instruction.
The Imam (‘a) was the man to whom the ruling leadership resorted for consultation and authority when they wished to solve some difficult problems, which they could not solve themselves. But we cannot find a single instance in the history of the Islamic experience during the time of the four caliphs in which the Imam turned to someone else for an opinion as to the way in which a problem should be dealt with according to Islam. On the other hand, there were tens of instances in which the ruling Islamic leadership felt it necessary to consult the Imam in spite of their reservations towards him.
The above arguments along with the event of Ghadeer establish the fact that the successor of Prophet Muhammad was none other than Imam Ali (‘a). The Holy Prophet (S) himself, on the instructions of Almighty Allah, appointed him as his successor.
“O Messenger! Deliver what has been revealed to you from your Lord; and if you do it not, then you have not delivered His message, and Allah will protect you from the people; surely Allah will not guide the unbelieving people.” (5:67)
The above verse speaks about a revelation that is of so much paramount significance and quintessential that if it were not delivered, it would nullify all other efforts of the Holy Prophet(S). The verse was revealed in the later period of prophetic mission. So the question arises what is the message which is so essential and indispensable that if that is not conveyed, it will be tantamount to not conveying anything at all? By this time, most of the beliefs and rules of Islamic sharia have already been revealed and conveyed. So this message must be something other than that.
The verse says that Allah will protect the holy Prophet(S) from the people, following with the lack of guidance for those who disbelieve.
The question regarding the importance of the order from Allah (swt) has been answered by Allamah Tabatabai:
“Why was this order so important that if it was not conveyed then the message was not conveyed at all? It was because religion’s knowledge and commands are inter linked…The fact, that if this commandment was not conveyed, then no other order was conveyed, shows its utmost importance, and makes it crystal clear that this particular order occupies such a central position in the whole structure that if it was left unannounced, it would amount to leaving all other orders unannounced, because its relation to other items is like that of soul with body; if it is disconnected, there would remain only a dead body, devoid of feeling, movement (and perception, etc.)…there was a danger that the people would oppose it and strive hard to overturn it against the Prophet (S) aiming at demolishing the structure of religion he had built and disintegrating all its parts…Accordingly, he kept postponing its delivery from time to time, waiting for a suitable circumstances and peaceful atmosphere, in order that his mission might be successful and his endeavors fruitful. But Allah ordered him to make haste in conveying that message, showing to him its importance, and promising to protect him from the people.”
The verse makes it clear that the Holy Prophet (S) was going to convey something on the order of Allah which might incite opposition. What was the message that Holy Prophet(S) was supposed to convey that would provoke the people, specifically, the disbelievers? As per numerous traditions from both Shia and Sunni sources, it was about guardianship of Imam Ali (‘a). It was about the issue of successorship after the death of Holy Prophet(S) and leadership and guardianship of the Islamic nation.
The issue of guardianship is so important that without it, not only religion would be in complete, but without it the non-believers would have been successful in their plots against the Divine Religion.
The Holy Prophet (S) conveyed this message after performing his last Hajj. He ordered Muslims to assemble at the pond of Ghadeer, it was there he announced the guardianship of Imam Ali (‘a):
It has been narrated from Abi Sa’id that: “When the day of Ghadeer Khumm came, the messenger of Allah (S) commanded the caller to call out, ‘Gather for the prayer. Then he took Ali (‘a) by the hand and said, ‘O’ Allah! Whomsoever I am his master, this Ali is also his master. O’ Allah! Be a friend to that person who is a friend to him, and be an enemy to that person who is an enemy to him.’” 
With the announcement of guardianship, the message of Islam was perfected and completed. The non-believers who have been hatching conspiracies to overturn Islam and revert the people to the polytheism became disappointed. Allah (swt) accepted the mission of Holy Prophet(S) and gave His seal of approval upon Prophet Muhammad’s (S) deliverance:
“This day have those who disbelieve despaired of your religion, so fear them not, and fear Me. This day have I perfected for you your religion and completed My favor on you and chosen for you Islam as a religion” (5:3)
For more information about the event of Ghadir, read:
 Ref: Sahih, Bukhari, Chapter: About the saying of the sick, vol 2, Sahih, Muslim, End of the book of al Wasiyyah, vol 5 p 75, Musnad, Ahmed, vol 1 p 335, vol 5 p 116 Tarikh, Tabari, vol 3 p 193, Tarikh, Ibn al Athir, vol 2 p 320. For the whole story of the event, read:
 Hadith cited in “A Study on the Question of Al-Wilaya”, by As-Shahid Ayatullah Muhammad Baqir al-Sadr: https://www.al-islam.org/ghadir-muhammad-baqir-al-sadr-sachedina-muhammad-rizvi-husein-khimjee/chapter-1-study-question-al
 Al Mizan, Exegesis of verse 67 of surah Maida
 Biharul Anwar, Volume 37, Hadith 4, as quoted in “Forty Ahadith on Ghadir” by Mahmud Sharifi https://www.al-islam.org/forty-ahadith-ghadir-mahmud-sharifi