Fadak was a village in Hijaz. Between fadak and Medina there was a distance of two days.It was a jewish land in the begining of its history.1 It was inhabited by some Jews untill the seventh year of hijra when Allah cast terror into their hearts and they made peace with the prophet by giving him a half of Fadak.Also it was mentioned that they gave him the entire Fadak.2
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1- Mu'jamul Buldan by Yaqout al-Hamawi,vol.4 p.238-239.
2- Refer to Futoohul Buldan by al-Balatheri p.42-46 to see that the people of Fadak and made peace with the prophet for the half of Fadak and that it was a pure property of the prophet because he did not get it by war to be considered as booty for the Muslims.In page 46 the author said: "In two hundred and ten hijra the Abbasid caliph al-Ma'moon hin Haroon ar-Rasheed paid it back to the Fatimites.He wrote to his wali of Medina Qathm bin Ja'far ordering him to do that.