Omar-ibn-Khattab narrates that the Messenger of Allah (ص) said:
"O Ali, you are the first Muslim to embrace Islam, and you are the first of the believers"
Dailami, Firduas Al-Akhbar, V.5, page 406; Ibn Asaker, Tarikh Madinah-Damishq, V.42, page 167; Ibn Marduyeh Esfahani, Al-Manaqib, page 50.
Ibn Asaker has narrated from Habbah bin Juwayn al-Urani who said: I heard Ali ibn Abi Talib say, “I am the first person to have believed in the Messenger of Allah (s.a.w.a.) or to have prayed with him.” (Tarikh Madinah-Damishq V.42, page 30-31). The contents of the aforesaid hadith have been stated on a wide scale