Sayyiduna Jabir bin Samurah (may Allah be pleased with him) said: I heard the Prophet (peace and blessings be upon him) say: "This matter (the religion) will always remain established; a group of the Muslims will keep fighting for its sake until the Hour is established."
Hadith Referenceالمعجم الكبير للطبراني / باب الجيم / 1998