Abu Dawud Book 21, Hadith Number 3833.

Narated By AbuHurayrah : The Prophet (PBUH) said: When a mouse falls into clarified butter, if it is sold, throw the mouse and what is around it away, but if it is in a liquid state, do not go near it. Al-Hasan said: AbdurRazzaq said: This tradition has been transmitted by Ma’mar, from az-Zuhri, from Ubaydullah ibn Abdullah ibn Abbas, from Maymunah, from the Prophet (PBUH).