I know that when I confront them with this warning...

I know that when I confront them with this warning, I will not like their response." Then Prophet invited the members of his clan to dine with him on a small amount of food and little milk. There were forty of them. After they ate, the Prophet spoke to them: "O Children of Abdul Muttalib, by God, I do not know of any young man from the Arabs who brought to his people better than I brought to you. I have brought to you the goodness of this world and the Hereafter.

The Almighty commanded me to invite you to it. Who among you will assist me on this mission and become my brother, my executor, and my successor?" No one accepted the invitation, and I said: "O Messenger of God, I shall be your assistant." He held my neck and said to them: "This is my brother, my executor (Wasi), my successor (Caliph) among you. So listen to him and obey him." They laughed, saying to Abu Talib: He (Muhammad) commanded you to listen to your son and to obey him.

Sunni References: (1) History of Tabari, English version, v6, pp 88-92 (two traditions) (2) History of Ibn Athir, v2, p62 (3) History of Ibn Asakir, v1, p85 (4) Durr al-Manthur, by al-Suyuti, v5, p97 (5) al-Sirah al-Halabiyah, v1, p311 (6) Shawahid al-Tanzil, by al-Hasakani, v1, p371 (7) Kanz al-Ummal, by al-Muttaqi al-Hindi, v15, p15, pp 100-117 (8) Tafsir al-Khazin, by Ala-ud-Din al-Shafi'i, v3, p371 (9) Dala'il al-Nabawiyah, by al-Baihaqi, v1, pp 428-430 (10) al-Mukhtasar, by Abul Fida, v1, pp 116-117 (11) Life of Muhammad, by Hasan Haykal, p104 (First Edition only.

In the second edition the last sentence of Prophet (PBUH) has been removed.) (12) Tahdhib al-Athar, v4, pp 62-63. The above tradition was also reported by important Sunni figures such as Muhammad Ibn Is'haq (who is the most celebrated Sunni historian), Ibn Abi Hatem, and Ibn Mardawayh. It is also recorded by orientalists such as T. Carlyle, E. Gibbon, J. Davenport, and W. Irving.

Here we would like ask the following question: Imam Ali reported that the Messenger of God is the one who granted him the office of executorship, brotherhood, and successorship. Sayf Ibn Umar reported that the idea of the executorship of Ali had came from a Jew called Abdullah Ibn Saba. We should ask the members of the Takfeer University (who call everyone who disagree with them unbeliever) the following question: Do you believe in Imam Ali's report or Sayf Ibn Umar's?

Sayf was accused by prominent Sunni scholars of weakness, forgery, and heresy.