Musannaf Ibn Abi Shayba 35:176

Abu Usama narrated to us, from Ubaydullah ibn Umar, from Sa'id ibn Abi Sa'id, from Abu Hurayrah, who said: The Prophet (peace and blessings of Allah be upon him) said: "Indeed, Allah has forbidden, upon my tongue, what is between the two lava fields (labbatan) of Medina."