One-fifth of Booty to the Cause of Allah (Khumus)
حَدَّثَنَا مُحَمَّدُ بْنُ سِنَانٍ، حَدَّثَنَا هُشَيْمٌ، أَخْبَرَنَا سَيَّارٌ، حَدَّثَنَا يَزِيدُ الْفَقِيرُ، حَدَّثَنَا جَابِرُ بْنُ عَبْدِ اللَّهِ ـ رضى الله عنهما ـ قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " أُحِلَّتْ لِي الْغَنَائِمُ ".Narrated Jabir bin `Abdullah:Allah's Messenger (ﷺ) said, "Booty has been made legal for me
From Sahih al-Bukhari, whose reports the scholars accept as authentic.