The properties of Banu Nadir were among what Allah granted as spoils to His Messenger ﷺ, for which the Muslims had not driven any horses or camels. They belonged exclusively to the Messenger of Allah ﷺ. He would spend from them on his family's annual maintenance, then allocate what remained for weapons and mounts as preparation for the cause of Allah.
كانت أموال بني النضير مما أفاء الله على رسوله ﷺ مما لم يوجف المسلمون عليه بخيل ولا ركاب، فكانت لرسول الله ﷺ، خاصة، وكان ينفق على أهله نفقة سنته، ثم يجعل ما بقي في السلاح والكراع عدة في سبيل الله.
Bukhari narrated it in jihad and expeditions (2904), and Muslim in jihad and expeditions (1757: 48), both of them by way of Sufyan (he is Ibn Uyayna), from Amr (he is Ibn Dinar), from Zuhri, from Malik bin Aws, from Umar, who related it.