‘Ubādah ibn as-Sāmit (may Allah be pleased with him) reported: We pledged allegiance to the Messenger of Allah (may Allah's peace and blessings be upon him) to listen and obey at times of hardship and ease, energy and reluctance, and to endure if prejudice is held against us, and not to fight those in authority for power, and to say the truth wherever we are, without fearing anyone's reproach for the sake of Allah.
The Prophet (may Allah's peace and blessings be upon him) took the pledge of allegiance from the Companions over obedience to the rulers in what is easy and what is hard and in the state of richness and poverty, and whether they like or dislike their commands; even if the rulers prefer themselves over the subjects concerning the public funds, positions, and the like, they should listen and obey them in what is good and not revolt against them. This is because the strife and corruption that would result from fighting them are worse than the corruption caused by their oppression. Among the things they pledged allegiance to is to speak the truth wherever they may be, being sincere to Allah and not fearing those who reproach them.