On the day when Mecca was conquered the Prophet ordered the idols to be broken. The idol “Hubal” was the largest idol in Mecca, a giant stone statue placed on the top of the Ka’bah. There are reports that initially the Prophet (sawa) was going to climb onto the shoulders of Ali (as), but allegedly Ali (as) did not have the strength to carry him. Following the command of the Holy Prophet, `Ali placed his feet on the Prophet’s shoulders to climb to the top of the Ka’bah, and pull “Hubal” from its place and cast it down. What is the reason that Ali (as) could not carry the Prophet (sawa) but rather it was the Prophet (sawa) who was to carry Ali (as) ?

‘I asked Ja’far bin Muhammad (as), ‘O son of Rasool-Allah! I have within myself, a certain question which I want to ask you about’. So he said; ‘If you like I would inform you of your questions before you even ask me, and if you so like, then ask’.
I said, ‘O son of Rasool-Allah! And by which thing do you recognise what is within myself before I even ask you?’ He said: ‘By expectation and insight. Have you not heard the Words of Allah Mighty and Majestic “Surely in this are signs for those who examine” (15:75), and the words of Rasool-Allah: ‘Fear the insight of a Believer for he looks by the Light of Allah?’ I said, ‘O son of Rasool-Allah, so inform me regarding my questions’.
He (as) said: ‘You intend to ask me about Rasool-Allah as to why did he carry Ali bin Abu Talib (as) to bring down the idols from the surface of the Ka’bah (as opposed to him carrying the Prophet), when he (as) had the strength and the intensity which he displayed when he ripped off the door of the fort of Khaybar and threw it behind him to a distance of forty cubits, and it was not being carried by forty men, and Rasool-Allah had ridden upon the camel, and the horse, and the mule, and rode upon Al-Buraaq on the night of the Ascension (المعراج ), and all that was lower than Ali in strength and intensity?’ I said, ‘By Allah, this is what I intended to ask you, O son of Rasool-Allah, so inform me’.
So he (as) said: ‘Ali (as) had nobility with Rasool-Allah, and by it he was raised to extinguish the fire of Polytheism, and invalidate every worshiped one besides Allah Mighty and Majestic. And had the Prophet (sawa) been raised for the bringing down of the idols, it would have been by Ali that he would have been raised, and been ennobled, and arrived to the bringing down of the idols. And that was like that, he (as) would have been higher than him (sawa). Have you not seen that Ali (as) said: ‘When I was raised upon the shoulders of Rasool-Allah, I was ennobled and raised to the extent that if I had so desire to, I would have touched the sky.
But, do you know that the Lantern it which guides in the darkness, and its emission is a branch of the original source. And Ali (as) said: ‘I am from Ahmad like the Illumination is from the illumination’.
But, do you know that Muhammad (sawa) and Ali (as) were two Lights in front of Allah Mighty and Majestic before the Creation of the creatures, by two thousand years, and that the Angels, when they saw that Light, saw it as original from which was radiating a blinding radiance, so they said: ‘Our Allah, and our Master! What is this Light?’ So Allah Blessed and High Revealed unto them: “This is a Light from My Light. Its root is Prophet-hood and its branch is Imamate. As for the Prophet-hood, so it is for Muhammad, My servant, and My Messenger. And as for the Imamate, so it is for Ali, My Proof, and My Guardian. And had it not been for these two, I would not have Created My creation”.
But do you know that Rasool-Allah (sawa) raised the hand of Ali at Ghadeer Khumm, to the extent that the people looked at the whiteness of his two arms. So he was made to be a Master of the Muslims and their Imam.
And he had carried Al-Hassan (as) and Al-Husayn (as) on the day of Hazeera of the Clan of Najjar. So when one of his companions said, ‘Let me carry one of them, O Rasool-Allah’, he said: ‘These two are the best of the riders and the father of these two is better than these two’.
And he was Praying with his companions, so he prolonged a Prostration from his Prostrations. So when he greeted (at the end of the Prayers), it was said to him, ‘O Rasool-Allah! You have prolonged this Prostration’. So he said: ‘My two son were riding upon me, so I disliked that I should hasten them, until they descended (by themselves)’. But rather, what he intended by that was to raise them, and their nobility. So the Prophet was an Imam and a Prophet, and Ali was an Imam and neither a Prophet nor a Rasool.
Muhammad bin Harb Al-Hilaly said, ‘So I said to him (as), ‘O son of Rasool-Allah! Increase it for me’ (tell me more). So he said: ‘You are indeed deserving of the increase’.
Rasool-Allah carried Ali upon his shoulders, intending by that, that he (as) was the father of his (grand) sons, and an Imam from the Imams from his back, just as overturning of his cloak during the Prayer of Al-Istiqsa’a (the rain), it is intended by that it be known by his companions, that he had overturned the famine’.
He (the narrator) said, ‘I said to him, ‘Increase it for me (tell me more), O son of Rasool-Allah’.
So he said: ‘Rasool-Allah carried Ali, intending by that to let his people know that he would lighten from the shoulders of Rasool-Allah, what is upon him from the debts and the fulfillment of the promised made, from after him’.
He (the narrator) said, ‘I said to him, ‘O son of Rasool-Allah, Increase it for me’ (tell me more).
So he said: ‘He (sawa) carried him (as), to it would be known by that he has carried him, and has not carried except that he was Infallible (sinless), and he has not carried a burden, so that his action would become one of wisdom, and correct. And the Prophet had said to Ali: ‘O Ali! Allah Blessed and High Loaded me with the sins of your Shia, then Forgave them for me, and these are the Words of the High That Allah may Forgive you what has preceded from your sins and what is to follow. (48:2)
And when Allah Mighty and Majestic Revealed when you are on the right way (5:105), and Ali is my own self, and my brother. Obey Ali, for he is Purified, Infallible, does not stray nor has he a parallel’. Then he recited this Verse Say: Obey Allah and obey the Rasool; but if you turn back, then on him rests that which is imposed on him and on you rests that which is imposed on you; and if you obey him, you are on the right way; and nothing rests on the Rasool except for the clear delivery’. (24:54)
Muhammad bin Harb Al-Hilaly said, ‘Then Ja’far bin Muhammad (as) said: ‘O you Emir! If I were to inform you with what (all) the intended meanings were with regards to the Prophet carrying Ali during the bringing down of the idols from the roof of the Kaaba, you would say that Ja’far bin Muhammad (as) is insane. Therefore, let it suffice, what you have heard’.
So he stood up and kissed his forehead and said, Allah Knows best where He Places His Message’. (6:124)

Sanad: Abu Ali Ahmad bin Yahya Al Maktab narrated to us, from Ahmad bin Muhammad Al Waraq, from Bishr bin Saeed bin Qalbawayh, the revisionist at Rafaqa, from Abdul Jabbar bin Kaseer Al Tameemi who said, ‘I heard Muhammad bin Al Hilali, the Emir of Al Medina saying the above hadith

Source: `ilal al-Shara’i`, Sh. al-Sadooq, Volume 1, Chapter 139, Hadith #1 (see Image below)