Sunan an-Nasa'i 4142
It was narrated that 'Ata' said concerning the saying of Allah, the Mighty and Sublime:
"And know that whatever of  spoils of war that you may gain, verily, (1/5th) of it is assigned to Allah, and to the Messenger, and to the near relatives (of the Messenger (Muhammad)" "The Khumus (one-fifth)  of Allah and of His Messenger is the same. The Messenger of Allah used to provide mounts (for jihad) with it, and give some (to the poor), and distribute it however he wanted, and do with it whatever he wanted."
أَخْبَرَنَا عَمْرُو بْنُ يَحْيَى، قَالَ حَدَّثَنَا مَحْبُوبٌ، قَالَ أَنْبَأَنَا أَبُو إِسْحَاقَ، عَنْ زَائِدَةَ، عَنْ عَبْدِ الْمَلِكِ بْنِ أَبِي سُلَيْمَانَ، عَنْ عَطَاءٍ، فِي قَوْلِهِ عَزَّ وَجَلَّ ‏{‏ وَاعْلَمُوا أَنَّمَا غَنِمْتُمْ مِنْ شَىْءٍ فَأَنَّ لِلَّهِ خُمُسَهُ وَلِلرَّسُولِ وَلِذِي الْقُرْبَى ‏}‏ قَالَ خُمُسُ اللَّهِ وَخُمُسُ رَسُولِهِ وَاحِدٌ كَانَ رَسُولُ اللَّهِ صلى الله عليه وسلم يَحْمِلُ مِنْهُ وَيُعْطِي مِنْهُ وَيَضَعُهُ حَيْثُ شَاءَ وَيَصْنَعُ بِهِ مَا شَاءَ ‏.‏