Husain Ibn Ali (a.) reported that the Prophet Muhammad (s.) said: “Whoever saw an unjust ruler who allows what God forbids and breaks the covenant of God and contradicts the custom (Sunnah) of His Messenger and treats the servants of God in a sinful and hostile manner and does not change them by word and deed, God has the right to let him enter where he will let the ruler enter.” [Bihar-ul-Anwar of Al-Majlisi, Volume 44 page 382]
عن الحسين بن علي عليه السلام عن النبي صلى الله عليه وآله وسلم قال: من رأى سلطانا جائرا مستحلا لحرم الله ناكثا لعهد الله مخالفا لسنة رسول الله يعمل في عباد الله بالاثم والعدوان ثم لم يغير بقول ولا فعل كان حقيقا على الله أن يدخله مدخله
Muhammad Baqir reported that Ahmad Ibn Ali said: “Umar Ibnu l-Khattab used to deliver a sermon to the people on the pulpit of the messenger (s.) and he mentioned in his sermon that he was more entitled to the believers (33:6) than to themselves, to which Husain (a.) said to him from the direction of the prayerhouse: “O Liar, come down from the pulpit of my Father, the Messenger of God! It is not the pulpit of your father!” Umar said to him: “By my life, so it is the pulpit of your father, O Husain, not that of my father? Who taught you that? Your father Ali Ibn Abi Talib?” Husain (a.) said to him: “If I obey my father in what he commanded me and by my life, he is a guide, so i am guided through him, and the oath of allegiance to him is by the covenant of the messenger with whom Gabriel (a.) came down from Allah, on the neck of men. No one rejects this except he who denies the Book! People recognized him with their hearts, but they rejected him with their tongues, so woe to those who reject the right of us who belong to the people of the house, because of that whereby the Messenger (s.) meets them in constant anger and severe punishment.” Umar said: “O Husain! whoever rejects the right of your father, may god curse him! The people chose us as the commanders, and so we took command over them, but if they had chosen your father as the commander, we would have obeyed.” Husain (a.) said to him: “O son of Khattab, which of the people chose you as their commander before you chose Abu Bakr as your commander, so that without proof from the Prophet and without the satisfaction of the family of Muhammad (s.), he might appoint you as the commander of the people? Should your satisfaction lead to the satisfaction of Muhammad (s.) or to the satisfaction of its people to his wrath? By God, when there is a statement on the tongue then its affirmation is prolonged and in fact it supports the believers. When one climbed over the necks of the family of Muhammad (s.) and ascended to their pulpit and when the judge turned against you with a book that came down in your midst, you had no idea of its collection, nor did you know its interpretation, except the hearing of the call to prayer. The one who fails and the one who strikes are the same with you. May God reward you with what you deserve and confront you with a exposing questioning.” Thereupon Umar descended in anger while a group of his companions went with him until they came to the door of the Commander of the Believers (a.) Umar asked for permission to enter, and when he gave him permission, he said: “O father of Hasan, what did i meet from your son Husain? He raises his voice against us in the prayerhouse of the messenger and incites the people and the inhabitants of Medina against me!” Hasan (a.) said to him: “Someone like Husain, the son of the Prophet (s.), provokes those to whom does not belong the judgement or he speaks to the people with regards to the people of his religion, but by God, you did not achieve what you came to except through the people and God curse those who have stirred up the people!” Thereupon the commander of the believers (a.) said to him: “Gently, O Father of Muhammad! Neither will you be close to resentment, nor of a lowly origin, nor will the veins from Sudan run in you. Listen to my words and do not be hasty with your words.” Umar said to him: “O father of Hasan, they are dealing with something that cannot be seen without the successorship.” The commander of the believers (a.) said to him: “They are from the lineage even closer to the Messenger (s.) than their fathers. But make them satisfied with their right, and he will be satisfied with you after them.” Umar said: “What is their satisfaction, O father of Hasan?” Ali (a.) said: “Their satisfaction consists in resignation from transgression and fear of transgressing through repentance. Umar said to him: “Rebuke your son, O father of Hasan, lest he fall into the hands of the rulers who are the judges on earth!” Ali (a.) said to him: “Rather I rebuke the people of transgression for their disobedience and those for whom I fear error and ruin, but as for him whom the Messenger (s.) brought into the world, it is not permissible for me to rebuke him, for he went over to a behaviour that is better for him, so make them both satisfied, O son of Khattab!” Thereupon Umar went away and Uthman Ibn Affan and Abd-ur-Rahman Ibn Awf came to meet him. Abd-ur-Rahman said to him: “O father of Hafs, what have you done so that the argument with you dragged on?” Umar said to him: “Can there be any argument against the son of Abu Talib and his two young lions?” Uthman said to him: “O son of Khattab, they are the obese sons of Abd Manaf, while the people are lean!” Umar said to him: “I will not mention where you went with pride, so that you fell because of it or because of your stupidity?” Then Uthman reached for his robe and he pulled it and pushed it back. Then he said: “O son of Khattab, it seems you disagree with what i say.” Abd-ur-Rahman Ibn Awf went between them and separated them, and the people went their ways.” [Bihar-ul-Anwar of Al-Majlisi, Volume 30 pages 47-50]