Sahih Muslim
The Book on Government (Kitab Al-Imara)
Book Number: 020 / Hadith Number: 4716
It has been narrated on the authority of Mughira who said: I heard the Messenger of Allah (may peace be upon him) say: A group of people from my Umma will continue to be triumphant over the people until the Command of Allah overtakes them while they are still triumphant. The same tradition has been narrated through another chain of transmitters on the same authority.