The First Verse: Allah says:
﴾O Apostle! 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)﴿
This Qur’anic verse had descended in order to reveal Imam Ali’s guardianship. This fact has been mentioned in the books of the Sunnis. The author of Al-Ghadir has quoted this in vol.1 p. 214 -223 from thirty of their books.
The Second Verse: Allah says:
﴾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)﴿
Al-Amini, in his book Al-Ghadir, vol. 1 p. 230, has quoted the narrations that confirm that this verse concerned the divine leadership of Imam Ali from sixteen books of the Sunnis.
The Third Verse: Allah says:
﴾A questioner asked about a chastisement, about to fall for the unbelievers. There is none to avert it from Allah, the Lord of the ways of Ascent. (70:1-3)﴿
This verse was revealed because someone, when he heard the Prophet saying, "Of whomsoever I had been guardian, Ali here is to be his guardian,"- said, 'O Allah, if what Muhammad is saying is true, let heaven send stones upon us.'
A little after that Allah sent down a stone on his head and killed him. Then Allah revealed this verse to Prophet Muhammad (PBUH). Al-Amini quoted that in his book Al-Ghadir, vol.1 p. 239 -246 from thirty of the books of the Sunnis.
The Companions Pay Homage to Imam Ali and Congratulate him
"Then people began to say, 'yes, we have heard and obeyed the order of Allah and his Messenger with our hearts.' The first of those who shook hands with Prophet Muhammad (PBUH) and Imam Ali were Abu Bakr, Umar, Uthman, Talha, az-Zubeir, the rest of the Muhajirs (emigrants), the Ansar (helpers) and the public.They continued this until the Prophet (PBUH) led them in the congregational Zhuhr (noon) Prayer and the Asr (afternoon) Prayer combined. They kept on doing this until he (PBUH) led them in congregational Maghrib (sunset) Prayer and the 'Isha' (evening) Prayer both of them also combined. Thus they carried on paying homage and shaking hands for three days."
The author of Al-Ghadir quoted, in vol. 1 p. 272, the news of Umar bin al-Khattab congratulating Imam Ali from sixty Sunni books.
* Source: imamreza.net