It was narrated that 'Umar said: "The wealth of Banu An-Nadir was among the Fay' that Allah bestowed upon His Messenger, in cases where the Muslims did not go out on and expedition with horses and camels. From it he kept for himself food for one year, and what was left he spent on cavalry and weapons equipment for the cause of Allah."
Source: sunnah.com
Other translations
Arabic
أَخْبَرَنَا عُبَيْدُ اللَّهِ بْنُ سَعِيدٍ، قَالَ حَدَّثَنَا سُفْيَانُ، عَنْ عَمْرٍو، - يَعْنِي ابْنَ دِينَارٍ - عَنِ الزُّهْرِيِّ، عَنْ مَالِكِ بْنِ أَوْسِ بْنِ الْحَدَثَانِ، عَنْ عُمَرَ، قَالَ كَانَتْ أَمْوَالُ بَنِي النَّضِيرِ مِمَّا أَفَاءَ اللَّهُ عَلَى رَسُولِهِ مِمَّا لَمْ يُوجِفِ الْمُسْلِمُونَ عَلَيْهِ بِخَيْلٍ وَلاَ رِكَابٍ فَكَانَ يُنْفِقُ عَلَى نَفْسِهِ مِنْهَا قُوتَ سَنَةٍ وَمَا بَقِيَ جَعَلَهُ فِي الْكُرَاعِ وَالسِّلاَحِ عُدَّةً فِي سَبِيلِ اللَّهِ .
sunnah.com