Sahih Muslim Book 7, Hadith Number 3169.

Chapter : Eminence of Medina, Allah’s Apostle (may peace be upon him) showered blessings upon it. Its sacredness and unlawfulness of hunting and lopping of trees and demarcation its precincts.

Abu Huraira (Allah be pleased with him) reported that Allah’s Messenger (may peace be upon him) declared sacred the territory between two lava mountains of Medina. Abu Huraira said: If I were to find deer in the territory between the two mountains, I would not molest them, and he (the Holy Prophet) declared twelve miles of suburb around Medina as a prohibited pasture.