Khasa'is...
Khasa'is, by al-Nisa'i, p40 Musnad Ahmad Ibn Hanbal, v3, pp 32-33 Kanz al-Ummal, by al-Muttaqi al-Hindi, v6, p155 Majma' al-Zawa'id, by al-Haythami, v9, p133 Ahmad Ibn Hanbal and al-Hakim recorded with authentic document from Abu Said al-Khudri, that the Apostle of God said to Ali: "Verily you will do battle for (implementation of) the Quran, as you has done for its revelation." Sunni reference: Tarikh al-Khulafaa, by Jalaluddin al-Suyuti, p173 al-Hakim recorded that Anas Ibn Malik narrated that the Holy Prophet said to Ali: " You shall inform my nation about the truth and what they dispute after me": Sunni reference: al-Mustadrak, by al-Hakim, v3, p112, who wrote this is an authentic Hadith according to the stipulation of the two Shaikhs (al-Bukhari and Muslim).
[This would mean that the chain of narrators are considered to be authentic as stipulated by Bukhari and Muslim] The first Muslim It is an undisputed fact that Imam Ali was the first man to embrace Islam after the Holy Prophet (PBUH&HF). Below are some of the references Ibn Abi Shaybah and Ibn Asakir recorded on the authority of Salim Ibn Abi Jaad that he said: I asked of Muhammad Ibn Hanifah, "was Abu Bakr the first of the people to adopt Islam?" He replied: "No".
And Ibn Asakir on a reliable ascription from Muhammad Ibn Sa'd Ibn Abi Waqqas, that he said to his father Sa'd: "was Abu Bakr al-Siddeeq the first of you in embracing the faith?" He said: "No, for there were more than five people in faith before him" Ibn Kathir says: "it is clear that Muhammad's family believed before every other - his wife Khadija, his freedman Zaid and the Wife of Zaid Umm Ayman and Ali and Warakah." Sunni reference: Tarikh al-Khulafaa, by Jalaluddin al-Suyuti, p33 (History of the Caliphs translated by Major Barrett) It is also narrated that Anas Ibn Malik said: "The Messenger was commissioned on Monday and Ali believed in him on Tuesday." Sunni reference: al-Mustadrak, by al-Hakim, v3, p112 al-Hakim also narrated that: Salman al-Farsi said that the Messenger of God said: "The first one of you to drink from the Basin on the Day of Judgment is your first Muslim, Ali, the son of Abu Talib." Sunni reference: al-Mustadrak, by al-Hakim, v3, p112 Ibn Hisham recorded that: Ali Ibn Abi Talib was the first male to believe in the Messenger of God and that he prayed with him while he was only ten years old.