Musnad Ahmad 26:93

Abu Mu'awiyah narrated to us, Al-A'mash narrated to us, from Zayd ibn Wahb, from Abdullah, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "There will be rulers over you, and you will see selfishness." He said: They said: "O Messenger of Allah, what should one of us do if he reaches that?" He said: "Render the right that is upon you, and ask Allah for that which is yours."