Musannaf Ibn Abi Shayba 35:179

Yazid ibn Harun narrated to us, from Asim al-Ahwal, who said: I asked Anas ibn Malik, "Did the Prophet, may Allah bless him and grant him peace, make Medina a sanctuary?" He said, "Yes, it is a sanctuary. Allah and His Messenger have made it a sanctuary. Its vegetation must not be cut. Whoever does that, upon him is the curse of Allah, the angels, and all of mankind."