Sahih Bukhari, Chapter: Sales and Trade

Anas went to the Prophet with barley bread having some dissolved fat on it. The Prophet had mortgaged his armor to a Jew in Medina and took from him some barley for his family. Anas heard him saying, "The household of Muhammad did not possess even a single Sa of wheat or food grains for the evening meal, although he has nine wives to look after." (See Hadith No. 685)