Musnad Ahmad 33:289

Abu Mu'awiyah narrated to us, Al-A'mash narrated to us, from Abu Sufyan, from Jabir, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "When the caller to prayer (mu'adhdhin) gives the call, the Shaytan flees until he is at Al-Rawha." And it is thirty miles from Al-Madinah.