This story is beautiful.
Imam ibn Asakir relates in his book Tarikh Dimashq, that Mawla Ali ibn Abi Talib, Alayhis Salam, came to Sayyiduna `Umar ibn al-Khattab, Radi’Allahu Anhu, while he was sitting in his place of gathering for discussions [Majlis],
When Sayyiduna `Umar saw him he became extremely humble, then he moved to offer him a more comfortable place to sit.
Later on when Mawla ‘Ali left the gathering, some of the people and students asked Sayyiduna ‘Umar:
“Ya Amir Al-Mu’minin – O Leader of the Believers, it seems like you treat ‘Ali unlike anyone from among the Sahaba companions of our beloved Prophet, Sall’Allahu Alayhi wa Aalihi wa Sahbihi wa Sallam?”
Sayyiduna ‘Umar said to the man: “What are trying to say by that statement? Well, how do you think my behavior towards him was?”
The man said: “I noticed that whenever you would look at him, you then became overcome with emotion and you humbled yourself before him, choosing him over yourself because you are the one that moved to the side so that he may sit more comfortably than even yourself.”
Sayyiduna ‘Umar said,
“Again, what are trying to say by that, and so what, what do you care? There is nothing to prevent me from doing so?
By Allah, I swear by Allah that he is my master and the master [Mawla] of every believer for all time.”
– From the Virtues of Imam Ali ibn Abi Talib – Volume 1