Musnad Ahmad 907:208

Mu'awiyah ibn 'Amr narrated to us, Zaidah narrated to us, Simak narrated to us, from Jabir ibn Samurah, who said: I was informed that the Prophet, peace and blessings of Allah be upon him, said: "This religion will not cease to remain standing, a group of the Muslims will fight for it until the Hour is established."