Musnad Ahmad 33:619

Musa and Qutaybah narrated to us, they said: Ibn Lahi'ah narrated to us, from Abu al-Zubayr, from Jabir, that the Prophet, peace and blessings of Allah be upon him, said: "A rider will surely travel in the direction of Medina—Qutaybah said: in the side of Medina—and he will surely say: 'There was once in this place a large gathering of believers.'"