In the third year of his mission, when he was commanded to proclaim his prophethood openly, he appointed 'Ali, peace be upon him, as his successor. It is known that for the first three years of his prophetic mission, the Most Noble Messenger, peace and blessings be upon him and his family, did not make his summons public, instead calling people to Islam in secret. It was in the third year of his mission that he was instructed to invite his relatives to Islam openly.
He thereupon instructed 'Ali, peace be upon him, to invite forty of the leading personages of Quraysh to a banquet, and forty of the Prophet's relatives accepted. At their very first session, the nonsensical ravings of Abu Lahab, his raging anger and unbridled arrogance, caused the meeting to break up in confusion. The following day, when again everyone was gathered in accordance with the instructions of the Most Noble Messenger, peace and blessings be upon him and his family, first food was served to the guests, and then it was time for spiritual nourishment. The Prophet, peace and blessings be upon him and his family, stood up among his relatives, praised and supplicated the Creator, and said: "I swear that there is none worthy of worship other than the One God, and that I am His envoy to you and the entirety of mankind. I have brought you the means of felicity in both worlds. My Lord has commanded me to summon you to the religion of Islam, and I give you glad tidings that whoever among you accepts my summons the soonest and aids me in my mission will be my brother (akhi), my legatee (wasiyyi) and my successor (khalifati)."
Those words greatly disturbed those present at the gathering, for their pride was offended, and it almost seemed that the voice of truth and the summons of prophethood would remain unheeded. Suddenly 'Ali b. Abi Talib, peace be upon him, arose and cried out: "O Muhammad, I believe in the oneness of God and your messengerhood and I distance myself from the idol worshippers."
The Prophet, peace and blessings be upon him and his family, ordered 'Ali, peace be upon him, to sit down. He then repeated twice more his earlier proclamation, but those words of truth made no impact on the hearts of those gathered in that assembly. No one apart from 'Ali, peace be upon him, responded to the call of the Prophet, peace and blessings be upon him and his family. ''Ali's acceptance of that summons and his declaration of agreement with the Prophet, peace and blessings be upon him and his family, came at a time when he was just entering manhood. While everyone else sat voiceless and silent, he arose courageously and affirmed his acceptance of the Prophet's call a second time. Thereupon the Prophet turned to the assembly and said: "'Ali is my brother and legatee and my successor among you. Obey him, follow him, and pay heed to his words."
The reaction of the assembled guests was extremely hostile, for they wished to strip this declaration by the Prophet, peace and blessings be upon him and his family, of its effect, and they therefore stood up and quit the meeting in the most unworthy and discourteous fashion. This event constitutes one of the plainest and most significant chapters in history, and none of the well known historians has ever seen fit to deny its occurrence, Not even the most narrow-minded among them have been able to excise this historic occurrence from their writings.