Musnad Ahmad 30:636

'Abd al-Razzaq narrated to us, Ma'mar narrated to us, from al-Zuhri, from Ibn al-Musayyib, that Abu Hurayrah said: "The Messenger of Allah, peace and blessings of Allah be upon him, declared sacred what is between the two lava fields of Medina." Abu Hurayrah said: "If I were to find gazelles between its two lava fields, I would not startle them." And he made a sanctuary around Medina of twelve miles.