صحيح مسلم

It has been narrated on the authority of Umar, who said: The properties abandoned by Banu Nadir were the ones which Allah bestowed upon His Apostle for which no expedition was undertaken either with cavalry or camelry. These properties were particularly meant for the Prophet (ﷺ). He would meet the annual expenditure of his family from the income thereof, and would spend what remained for purchasing horses and weapons as preparation for Jihad.