O Messenger, announce that which has been revealed to you from your Lord, and if you do not, then you have not conveyed His message. And Allah will protect you from the people. Indeed, Allah does not guide the disbelieving people. [5/67]
Ten years after the migration, the Messenger of Allah ordered to his close followers to call all the people in different places to join him in his last pilgrimage. On this pilgrimage he taught them how to perform the pilgrimage in a correct and unified form.
This was first time that the Muslims with this magnitude gathered in one place in the presence of their leader, the Messenger of Allah. On his way to Mecca, more than seventy thousand people followed Prophet (PBUH&HF).
On the fourth day of Dhul-Hajjah more than one hundred thousand Muslims had entered Mecca.
Revelation of Verse 5:67
يا أَيُّهَا الرَّسُولُ بَلِّغْ ما أُنْزِلَ إِلَيْكَ مِنْ رَبِّكَ وَ إِنْ لَمْ تَفْعَلْ فَما بَلَّغْتَ رِسالَتَهُ وَ اللَّهُ يَعْصِمُكَ مِنَ النَّاسِ إِنَّ اللَّهَ لا يَهْدِي الْقَوْمَ الْكافِرينَ
O Messenger, announce that which has been revealed to you from your Lord, and if you do not, then you have not conveyed His message. And Allah will protect you from the people. Indeed, Allah does not guide the disbelieving people.
On the 18th of Dhul-Hajjah, after completing his last pilgrimage (Hajjatul-Widaa), Prophet was leaving Mecca toward Medina, where he and the crowd of people reached to a place called Ghadir Khum (which is close to today's Juhfah). It was a place where people from different provinces should say Good bye to each other and take different routes for their home. In this place, the following verse was revealed : "O Apostle! Deliver what has been sent down to you from your Lord; and if you don't do it, you have not delivered His message (at all); and Allah will protect you from the people ..." (Quran 5:67).
Some of Sunni references confirming that the revelation of the above verse of Quran was right before the speech of Prophet in Ghadir Khum:
(1) Tafsir al-Kabir, by Fakhr al-Razi, under commentary of verse 5:67,
v12, pp 49-50, narrated on the authorities of Ibn Abbas, al-Bara Ibn.
Azib, and Muhammad Ibn Ali.
(2) Asbab al-Nuzool, by al-Wahidi, p50, narrated on the authorities of
Atiyyah and Abu Sa'id al Khudri.
(3) Nuzul al-Quran, by al-Hafiz Abu Nu'aym narrated on the authorities.
Abu Sa'id Khudri and Abu Rafi.
(4) al-Fusool al Muhimmah, by Ibn Sabbagh al-Maliki al-Makki, p24.
(5) Durr al-Manthur, by al-Hafiz al-Suyuti, under commentary of verse 5:67.
(6) Fathul Qadir, by al-Shawkani, under commentary of verse 5:67.
(7) Fathul Bayan, by Hasan Khan, under commentary of verse 5:67.
(8) Shaykh Muhi al-Din al-Nawawi, under commentary of verse 5:67.
(9) al-Sirah al-Halabiyah, by Noor al-Din al-Halabi, v3, p301.
(10) Umdatul Qari fi Sharh Sahih al-Bukhari, by al-Ayni.
(11) Tafsir al-Nisaboori, v6, p194.
On this day the Messenger of Allah declared:
It seems the time approached when I shall be called away (by Allah) and I shall answer that call. I am leaving for you two precious things and if you adhere both of them, you will never go astray after me. They are the Book of Allah and my progeny, that is my Ahlul-Bayt. The two shall never separate from each other until they come to me by the Pool (of Paradise).
Then the Messenger of Allah continued:
Do I not have more right over the believers than what they have over themselves?" People cried and answered: "Yes, O' Messenger of God." Then Prophet held up the hand of Ali and said: "Whoever I am his leader (Mawla), Ali is his leader (Mawla). O' God, love those who love him, and be hostile to those who are hostile to him.
Some of the Sunni references:
(1) Sahih Tirmidhi, v2, p298, v5, p63
(2) Sunan Ibn Maja, v1, pp 12,43
(3) Khasa'is, by al-Nisa'i, pp 4,21
(4) al-Mustadrak, by al-Hakim, v2, p129, v3, pp 109-110,116,371
(5) Musnad Ahmad Ibn Hanbal, v1, pp 84,118,119,152,330, v4, pp 281,368,370,
372,378, v5, pp 35,347,358,361,366,419 (from 40 chains of narrators)
(6) Fada'il al-Sahaba, by Ahmad Hanbal, v2, pp 563,572
(7) Majma' al-Zawa'id, by al-Haythami, v9, p103 (from several transmitters)
(8) Tafsir al-Kabir, by Fakhr al-Razi, v12, pp 49-50
(9) Tafsir al-Durr al-Manthur, by al-Hafiz Jalaluddin al-Suyuti, v3, p19
(10) Tarikh al-Khulafa, by al-Suyuti, pp 169,173
(11) al-Bidayah wal-Nihayah, by Ibn Kathir, v3, p213, v5, p208
(12) Usdul Ghabah, by Ibn Athir, v4, p114
(13) Mushkil al-Athar, by al-Tahawi, v2, pp 307-308
(14) Habib al-Siyar, by Mir Khand, v1, part 3, p144
(15) Sawaiq al-Muhriqah, by Ibn Hajar al-Haythami, p26
(16) al-Isabah, by Ibn Hajar al-Asqalani, v2, p509; v1, part1, p319,
v2, part1, p57, v3, part1, p29, v4, part 1, pp 14,16,143
(17) Tabarani, who narrated from companions such as Ibn Umar, Malik Ibn
al-Hawirath, Habashi Ibn Junadah, Jari, Sa'd Ibn Abi Waqqas,
Anas Ibn Malik, Ibn Abbas, Amarah,Buraydah,...
(18) Tarikh, by al-Khatib Baghdadi, v8, p290
(19) Hilyatul Awliya', by al-Hafiz Abu Nu'aym, v4, p23, v5, pp26-27
(20) al-Istiab, by Ibn Abd al-Barr, Chapter of word "ayn" (Ali), v2, p462
(21) Kanzul Ummal, by al-Muttaqi al-Hindi, v6, pp 154,397
(22) al-Mirqat, v5, p568
(23) al-Riyad al-Nadirah, by al-Muhib al-Tabari, v2, p172
(24) Dhaka'ir al-Uqba, by al-Muhib al-Tabari, p68
(25) Faydh al-Qadir, by al-Manawi, v6, p217
(26) Yanabi' al-Mawaddah, by al-Qudoozi al-Hanafi, p297
... And many more..