It is narrated from Sayyiduna Abdullah bin al-Zubayr (may Allah be pleased with them both) that the Prophet (peace and blessings be upon him) allotted four shares for al-Zubayr (may Allah be pleased with him): "one share for his mother, one for him, and two shares for his horse."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب قسم الفيء والغنيمة / 12876