Musa bin Abi A'ishah (may Allah have mercy on him) said: I asked Yahya bin al-Jazzar (may Allah have mercy on him); I said: How much of the one-fifth was for the Messenger of Allah (peace and blessings be upon him)? He said: One-fifth of the one-fifth.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب قسم الفيء والغنيمة / 12940