Abu Huraira (may Allah be pleased with him) reports that the Messenger of Allah (peace be upon him) said: "No charity is obligatory upon a Muslim for his slave and his horse except for the charity of Fitr."
And the evidence that the Prophet, peace and blessings be upon him, only exempted charity from wealth in the case of slaves, and not the charity of al-Fitr.
Hadith Referenceصحيح ابن خزيمه / جماع أبواب صدقة المواشي من الإبل والبقر والغنم / 2288