Musnad Ahmad 32:420

Abu Amir narrated to us, Hisham narrated to us, from Qatadah, from Anas, "That he walked to the Prophet, may Allah bless him and grant him peace, with barley bread and rancid fat." He said: "And the Messenger of Allah, may Allah bless him and grant him peace, had pledged a shield of his to a Jew in Medina, and he took from him barley for his family." He said: And I heard him one day saying: "The family of Muhammad did not have a Sa' of grain, nor a Sa' of wheat in the evening, and he had nine wives at that time."