From what portion of the spoils of war (Ghanimah) is the voluntary gift (Nafil) distributed?

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The voluntary gift (Nafil) is taken from four-fifths of the spoils of war (Ghanimah). This is the stated position of Ahmad, Anas bin Malik, the jurists of Sham, including Raja' bin Haywah, 'Ubadah bin Nusay, 'Uday bin 'Uday, Makhul, Al-Qasim bin 'Abd al-Rahman, Yazid bin Abi Malik, Yahya bin Jabir, and Al-Awza'i. Ishaq and Abu 'Ubayd also hold this view. The evidence supporting this is the clear hadith stating, "There is no Nafil except after the Khums (one-fifth share)", reported by Abu Dawud and Ibn 'Abd al-Barr. Further evidence includes the hadith of Habib bin Muslimah, stating the Prophet (PBUH) used to give one-fourth or one-third as Nafil after the Khums, and the hadith of Jarir where 'Umar granted him one-third after the Khums. Furthermore, Allah the Almighty stated, "And know that whatever you take of a thing - indeed, for Allah is one-fifth of it..." (Quran 8:41), implying the Khums is taken from the entirety of the spoils, leaving four-fifths from which Nafil is taken. The action of the Prophet (PBUH) granting Salama bin al-Akwa' an extra share for a horseman, which was explicitly from the four-fifths, confirms this ruling.