Musnad Abu Ya'la al-Mawsili 6:95

Muhammad ibn Isma'il ibn Abi Samina narrated to us, 'Abd al-Wahhab narrated to us, Dawud narrated to us, from Abu 'Uthman, from Sa'd, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "The people of the West will continue to be manifest upon the truth until the Hour is established."