It is narrated from Ibn Abbas that the Messenger of Allah (ص) said:
“The forerunners in their faith in the Prophets] are three in number: the one who overwhelmed Moses (ع) and he is Joshua bin Nun; the forerunner in the nation of Jesus (ع) is Sahib Yasin; and the forerunner in the nation of Muhammad (ص) is Ali ibn Abi Talib (ع).”
Point No 1: Here, forerunners refer to those who superseded others in adoring the true religion.
Point No 2: Manawi says: Indeed, what a great virtue this is for Ali (ع) and also such other numerous outstanding qualities he possessed which others did not.
Haythami, Maj’mah al-Zawaid, V.9, page 102, narrated by Tabarani, Al-Mu’jam al-Kabir, V.11, page 77; Refer to Muttaqi Hindi, Kanz al-Ummal, V.11, page 601.