Sayyiduna Abu Hurayrah (may Allah be pleased with him) said that the Messenger of Allah (peace and blessings be upon him) said: "I have exempted you from the zakah of al-jabhah (horses), al-kus'ah (mules) and al-nukhkhah."
Baqiyyah (may Allah have mercy on him) said: Al-jabhah means horses, al-kus'ah means mules and donkeys, and al-nukhkhah means the slave-girls of the household.
Abu Mu'adh is Sulayman bin Arqam; he is matruk al-hadith (abandoned in hadith) and is not used as proof, and his chain for it is reported inconsistently: it is reported this way, and it is also reported from him, from al-Hasan, from Abd al-Rahman bin Samurah.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الزكاة / 7409