One-fifth of Booty to the Cause of Allah (Khumus)
حَدَّثَنَا يَحْيَى بْنُ بُكَيْرٍ، أَخْبَرَنَا اللَّيْثُ، عَنْ عُقَيْلٍ، عَنِ ابْنِ شِهَابٍ، عَنْ سَالِمٍ، عَنِ ابْنِ عُمَرَ ـ رضى الله عنهما أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم كَانَ يُنَفِّلُ بَعْضَ مَنْ يَبْعَثُ مِنَ السَّرَايَا لأَنْفُسِهِمْ خَاصَّةً سِوَى قِسْمِ عَامَّةِ الْجَيْشِ.Narrated Ibn `Umar:Allah's Messenger (ﷺ) used to give extra share to some of the members of the Sariya he used to send, in addition to the shares they shared with the army in general
From Sahih al-Bukhari, whose reports the scholars accept as authentic.