Sahih Muslim Book 20, Hadith Number 4719.

Chapter : Saying of the Holy Prophet (may peace be upon him): “A group of people from my Umma will always remain on the right path and continue to be triumphant.’ their opponents shall not be able to do them any harm.

It his been narrated on the authority of Umair b. Umm Hani who said: I heard Mu’awiya say (while delivering a sermon from the pulpit) that he heard the Messenger of Allah (may peace be upon him) say: A group of people from my Umma will continue to obey Allah’s Command, and those who desert or oppose them shall not be able to do them any harm. They will be dominating the people until Allah’s Command is executed (i.e. Resurrection is established).