The fourth incident was when this Holy Verse was revealed:

(Only Allah is your Vali and His Apostle and those who believe, those who keep up prayers and pay the poor-rate while they bow)_5;55.

The expositors mentioned that this Holy Verse was revealed because Ali (PBUH) gave his ring for charity to a poor man who later told the Prophet (PBUH) about it, the fact that made the Prophet (PBUH) exclaim ‘God is Great’ (Allah-o-Akbar).

There are many other incidents refer to Ali Bin Abi Talib (PBUH) as the Imam and the successor of the Prophet Mohammad (PBUH) and you can do your own research if you like to expand on this matter.

Anwar: What you presented was quite enough.

Hasan: Excellent. Let’s take a rest.