Sahih Muslim Book 7, Hadith Number 3176.

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.

Abd al-Rahman reported on the authority of his father Abu Sa’id (Allah be pleased with him) that he heard Allah’s Messenger (may peace be upon him) as saying: I have declared sacred what is between the two lava grounds of Medina just as Ibrahim (peace be upon him) declared Mecca as sacred. He (the narrator) then said: Abu Sa’id caught hold of (Abu Bakr, another narrator, used the word “found”) a bird in his hand and then released it from his hand and set it free.