One-fifth of Booty to the Cause of Allah (Khumus)
حَدَّثَنَا صَدَقَةُ، أَخْبَرَنَا عَبْدُ الرَّحْمَنِ، عَنْ مَالِكٍ، عَنْ زَيْدِ بْنِ أَسْلَمَ، عَنْ أَبِيهِ، قَالَ قَالَ عُمَرُ ـ رضى الله عنه لَوْلاَ آخِرُ الْمُسْلِمِينَ مَا فَتَحْتُ قَرْيَةً إِلاَّ قَسَمْتُهَا بَيْنَ أَهْلِهَا كَمَا قَسَمَ النَّبِيُّ صلى الله عليه وسلم خَيْبَرَ.Narrated Aslam:`Umar said, "Were it not for those Muslims who have not come to existence yet, I would have distributed (the land of) every town I conquer among the fighters as the Prophet (ﷺ) distributed the land of Khaibar
From Sahih al-Bukhari, whose reports the scholars accept as authentic.