I will be harsh and stern against the aggressor, but I will be a pillar of strength for the weak. I will not calm down until I will put one cheek of a tyrant on the ground and the other under my feet, and for the poor and weak, I will put my cheek on the ground.
'Umar asked 'Ali for the hand of his daughter, Umm Kulthum in marriage. 'Ali replied that she has not yet attained the age (of maturity). 'Umar replied, 'By Allah, this is not true. You do not want her to marry me. If she is underage, send her to me'. Thus 'Ali gave his daughter Umm Kulthum a dress and asked her to go to 'Umar and tell him that her father wants to know what this dress is for. When she came to Umar and gave him the message, he grabbed her hand and forcibly pulled her towards him. 'Umm Kulthum asked him to leave her hand, which Umar did and said, 'You are a very mannered lady with great morals. Go and tell your father that you are very pretty and you are not what he said of you'. With that 'Ali married Umm Kulthum to 'Umar.
Tarikh Khamees, Volume 2, p. 384 ('Dhikr Umm Kalthum') and Zakhair Al-Aqba, p. 168
Remember, I have not appointed you as commanders and tyrants over the people. I have sent you as leaders instead, so that the people may follow your example. Give the Muslims their rights and do not beat them lest they become abused. Do not praise them unduly, lest they fall into the error of conceit. Do not keep your doors shut in their faces, lest the more powerful of them eat up the weaker ones. And do not behave as if you were superior to them, for that is tyranny over them.
As quoted in Omar the Great : The Second Caliph Of Islam (1962) by Muhammad Shibli Numani, Vol. 2, p. 33
Take account of yourselves before your are brought to account.
I know that you are a Black Stone, you do not cause benefit or harm; and if it were not that I had seen Allâh’s Messenger – peace and blessings of Allâh be upon him – kiss you, I would never have kissed you.