Sahih Bukhari Volume 005, Book 057, Hadith Number 060.
Narated By 'Aisha : Fatima sent somebody to Abu Bakr asking him to give her her inheritance from the Prophet from what Allah had given to His Apostle through Fai (i.e. booty gained without fighting). She asked for the Sadaqa (i.e. wealth assigned for charitable purposes) of the Prophet at Medina, and Fadak, and what remained of the Khumus (i.e., one-fifth) of the Khaibar booty. Abu Bakr said, "Allah's Apostle said, 'We (Prophets), our property is not inherited, and whatever we leave is Sadaqa, but Muhammad's Family can eat from this property, i.e. Allah's property, but they have no right to take more than the food they need.' By Allah! I will not bring any change in dealing with the Sadaqa of the Prophet (and will keep them) as they used to be observed in his (i.e. the Prophet's) life-time, and I will dispose with it as Allah's Apostle used to do," Then 'Ali said, "I testify that None has the right to be worshipped but Allah, and that Muhammad is His Apostle," and added, "O Abu Bakr! We acknowledge your superiority." Then he (i.e. 'Ali) mentioned their own relationship to Allah's Apostle and their right. Abu Bakr then spoke saying, "By Allah in Whose Hands my life is. I love to do good to the relatives of Allah's Apostle rather than to my own relatives" Abu Bark added: Look at Muhammad through his family (i.e. if you are no good to his family you are not good to him).