Abu Sukheilah narrates: I went to Hajj with Salman aI-Farsi and on the way we stopped in Rabaza where Abu Dhar Al-Ghifaari was in exile (by the order of Usman b. Affan).

Abu Dharr said to us – There will be a dark conspiracy after my death, so hold on
to two things: the Qur’an and our master, Ali b. Abi Talib (a.s). I swear that I heard the Messenger of Allah (s.a.w.a.) say: Ali is the first one who believed in me and trusted me.

He is the first one who will shake my hand on the Day of Judgement.

He is Siddiq al-Akbar (the greatest truthful one), and he is the separator of right from wrong in this nation.

He is the leader of the believers, while wealth is the leader of the hypocrites.
Behaar al-Anwaar v 38 p 217