Sunnan Abu Dawud Collection: ::Book Number 19:: Hadith # 3010
Narrated Abdullah ibn AbuBakr: Abdullah ibn AbuBakr and some children of Muhammad ibn Maslamah said: There remained some people of Khaybar and they confined themselves to the fortresses. They asked the Apostle of Allah (peace_be_upon_him) to protect their lives and let them go. He did so. The people of Fadak heard this; they also adopted a similar way. (Fadak) was, therefore, exclusively reserved for the Apostle of Allah (peace_be_upon_him), for it was not captured by the expedition of cavalry and camelry.