Sahih Bukhari Volume 007, Book 067, Hadith Number 405.
Narrated By Salama bin Al-Aqwa' : In the evening of the day of the conquest of Khaibar, the army made fires (for cooking). The Prophet said, "For what have you made these fires?" They said, "For cooking the meat of domestic donkeys." He said, "Throw away what is in the cooking pots and break the pots." A man from the people got up and said, "Shall we throw the contents of the cooking pots and then wash the pots (instead of breaking them)?" The Prophet said, "Yes, you can do either."