Musnad Ahmad 33:563

Hassan narrated to us, Ibn Lahi'ah narrated to us, Abu al-Zubayr narrated to us, from Jabir, that the Messenger of Allah (peace and blessings of Allah be upon him) said: "A rider will surely travel along the side of the valley of Medina, and he will surely say: 'There was once in this place a large settlement of the believers.'"