The properties of Bam An-Nadir were among the booty that Allah gave to His Apostle such Booty were not obtained by any expedition on the part of Muslims, neither with cavalry, nor with camelry. So those properties were for Allah's Apostle only, and he used to provide thereof the yearly expenditure for his wives, and dedicate the rest of its revenues for purchasing arms and horses as war material to be used in Allah's Cause.
Sahih al-Bukhari, Vol. 6, Book of Prophetic Commentary on the Qur'an, Hadith 407
Sahih al-Bukhari, Book of Prophetic Commentary on the Qur'an, Hadith 407