Musnad Ahmed: Hadith 1605

The Messenger of Allah (ﷺ) said: I declare sacred what is between the two lava fields of Madinah as Ibraheem declared his sanctuary sacred. Its leaves are not to be cut down and its game is not to be killed. Nobody leaves it for lack of interest in it, but Allah will replace him with someone better than him. Madinah is better for them if they but knew. No one wishes ill to them (people of Madinah) but Allah will cause him to melt as lead melts in the fire and as salt dissolves in water.”