Sahih Muslim
The Book on Government (Kitab Al-Imara)
Book Number: 020 / Hadith Number: 4549
It has been narrated on the authority of Usaid b. Hudair that a man from the Ansar took the Messenger of Allah (may peace be upon him) aside and said to him: Will you not appoint me governor as you have appointed so and so? He (the Messenger of Allah) said: You will surely come across preferential treatment after me, so you should be patient until you meet me at the Cistern (Haud-i-Kauthar).