Sahih Bukhari
Virtues and Merits of the Prophet (pbuh) and his Companions
Volume: 004 / Book Number: 056 / Hadith Number: 835
Narrated Muawiya:
I heard the Prophet saying, "A group of people amongst my followers will remain obedient to Allah's orders and they will not be harmed by anyone who will not help them or who will oppose them, till Allah's Order (the Last Day) comes upon them while they are still on the right path."