'Umar (RAA) narrated, 'The wealth of Banu an-Nadir (one of the Jewish tribes) was part of what Allah bestowed on His Messenger , and which the Muslims had not ridden on horses or camels to get (i.e. they did not have to fight); so they belonged specially to the Prophet who would give his family their sustenance for a year, then applied what remained for horses and weapons and equipment in the Path of Allah, Who is Great and Glorious." Agreed upon.
English reference: Book 11, Hadith 1342
Arabic reference: Book 11, Hadith 1316