Sahih Muslim
The Book Pertaining to Piety and Softening of Hearts (Kitab Al-Zuhd wa Al-Raqaiq)
Book Number: 042 / Hadith Number: 7088
'A'isha reported: Never could the family of Muhammad (may peace be upon him) (afford to eat) the bread of wheat for two days successively. Even (out of these two days) one (was such wherein he could get) only a date.