The Book on Government (Kitab Al-Imara)
Muslim :: Book 20 : Hadith 4545
It has been narrated on the authority of 'Abdullah who said: The Messenger of Allah (may peace be upon him) said: After me there will be favouritism anad many things that you will not like. They (his Companions) said: Messenger of Allah, what do you order that one should do it anyone from us has to live through such a time? He said: You should discharge your own responsibility (by obeying your Amir), and ask God to cuncede your right (by guiding the Amir to the right path or by replacing him by one more just and God-fearing).