Sahih Muslim Book 7, Hadith Number 3158.

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.

Anas b. Malik reported a Hadith like this from Allah’s Apostle (may peace be upon him) except with this variation that he said: “I declare sacred the area between its two lava mountains.”