Certainly your Master is ...

بِسْمِ اللَّـهِ الرَّحْمَـٰنِ الرَّحِيمِ

Certainly your Master is Allah and His Messenger and those who believe who eshtablish prayer and give charity while they bow. And who ever takes Allah and His Messenger and those who believe as a guardian, so surely the party of Allah will be victorious. (Qur’an 5:55-56)

It is unanimous that the verse descended about Imam ‘Ali (as) when he gave away in charity his ring while he was in a state of kneeling in his prayer. This is also authenticated successively according to the 12 Imams. Here are some of the Shi’ite references

- Bihar al-Anwar, by Allama Majlisi

- Tafseer al-Mizan, by Allama Tabatabai

- Tafseer al-Kashaf, by Allama Muhammad Jawad Mughniyah

- al-Ghadir, by Allama Abdul Husayn Ahmad al-Amini

- Asbat al-Hudate, by Allama Muhammad Ibn Hasan Amuli

But for the sake of the readers I shall produce some Sunni references, and traditions in this respect through other sources. Many Sunni commentators of the Qur’an confirm the fact that the above verse descended on the honor of Imam ‘Ali (as) and many Sunni scholars have also mentioned the unanimity or consensus of opinion in their books. Here are some references in this regard:

(1) Tafsir al-Kabir, by Ahmad Ibn Muhammad al-Tha’labi, under Verse 5:55

(2) Tafsir al-Kabir, by Ibn Jarir al-Tabari, v6, pp 186,288-289

(3) Tafsir Jamiul Hukam al-Qur’an, by Muhammad Ibn Ahmad Qurtubi, v6, p219

(4) Tafsir al-Khazin, v2, p68

(5) Tafsir al-Durr al-Manthoor, by al-Suyuti, v2, pp 293-294

(6) Tafsir al-Kashshaf, by al-Zamakhshari, Egypt 1373, v1, pp 505,649

(7) Asbab al-Nuzool, by Jalaluddin al-Suyuti, Egypt 1382, v1, p73 on the authority of Ibn Abbas

(8) Asbab al-Nuzool, by al-Wahidi, on the authority of Ibn Abbas

(9) Sharh al-Tjrid, by Allama Qushji

(10) Ahkam al-Qur’an, al-Jassas, v2, pp 542-543

(11) Musnad Ahmad Ibn Hanbal, v5, p38

(12) Kanzul Ummal, by al-Muttaqi al-Hindi, v6, p391, Tradition #5991

(13) al-Awsat, by Tabarani, narrated from Ammar Yasir

(14) Ibn Mardawayh, on the authority of Ibn Abbas

... and more.

There is also a tradition related by Ibn Salam whose chain of sources rises up to the Prophet (S) himself. Please refer to the Sahih of Nisa’i or the commentary of Sura Ma’idah in Jam’a Bayn al-Sihah al-Sittah. In Ghayah al-Maram, p18, Sayyid al-Bahrayni forwards twenty four (24) traditions from sources other than the Ahlul-Bayt, all supporting the above fact.

For the sake of brevity, I am going to confine my self to a tradition occuring in the commentary of the Qur’an by Abi Is’haq Ahmad Ibn Muhammad ibn Ibrahim Nisaboori al-Tha’labi. A few comments on the respected personality: He died in 337 AH and Ibn Khallikan gives an account of his death saying: "He was unique as a commentator of the Qur’an and his Tafsir al-Kabir is superior to all other interpretations.”

When he reached this verse he recorded this in his Tafsir al-Kabir on the authority of Abu Dharr al-Ghifari, who said: Both of my ears may turn deaf and both of my eyes may become blind if I speak a lie. I heard the Messenger of Allah, Allah’s blessings and peace be upon him and his posterity, saying, "‘Ali is the guide of the righteous and the slayer of the infidels. he who has helped him is victorious and he who has abandoned him is forsaken.”

One day I said my prayers in the company of the Prophet. A beggar came to the mosque and begged for alms, but nobody gave him anything. ‘Ali was in a state of kneeling in the prayer. He pointed out his ring to the beggar, who appraoched him and removed the ring from his finger. Thereupon the Prophet, Allah’s blessings and peace be upon him and his posterity, implored Allah the Mighty and Glorious, saying: "O Allah! My brother Moses begged you saying, ‘My Lord, delight my heart and make my task easy and undo the knot in my tongue so that they may understand me, and appoint from my kinsmen, Haroon, my brother, as my vizier, and strenghthen my back with him and make him participate in my mission so that we may glorify You and remember You more frequently. Certainly You see us.’ And You inspired him: ‘O Musa! All your requests have been granted.’ O Allah! I am your slave and your prophet. Delight my heart and make my task easy and appoint from among my kinsmen ‘Ali as my vizier and strengthen my back with him."

Abu Dharr, then, proceeded By Allah, the Messenger of Allah, Allah’s blessings and peace be upon
him and his posterity had not yet finished his supplication when the trustworthy Gabriel descended to him with this Verse "Certainly Allah is Your Master, and His Prophet and those who believe
who establish prayer and give charity while they bow. And whoever takes Allah and His Messenger and those who believe as a guardian, so surely the party of Allah will be victorious."

Sunni reference: Tafsir al-Kabir, by al-Tha’labi under the commentary of verses 5:55-56 of Qur’an.

A Few Comments By The Other Commentators

Allama al-Tabarsi, while commenting on this verse in Majma’ al-Bayan states: "The plural form has been used for ‘Ali, Commander of the faithful, in order to express his honor and eminence.”And masters of the Arabic language use the plural form for an individual to show respect.

Allama al-Zamakshari in his Tafsir al-Kashshaf, has mentioned another nice point which is as follows:

If you inquire how this plural word is applicable to ‘Ali, may Allah be gracious to him, who is an individual, I shall say that though this verse is about ‘Ali, an individual, the plural form is used in order to presuade others to act similarly and to give alms as readily as ‘Ali did.

There is also an implied instruction that the faithful should keep themselves always on the look out for occasions of acts of sympathy, benevolence and charity to the poor and the needy, and readily do the needful without waiting till the completion of even so important a duty as saying a prayer.

Sunni reference: Tafsir al-Kashshaf, by al-Zamakhshari, v1, p649

Please refer to the Part II of the article of Ghadir Khum for further argument in this regard.