Musnad Ahmad 937:267

Muhammad ibn Bakr narrated to us, Ibn Jurayj informed us, from ‘Imran ibn Abi Anas, it reached him from him, from Malik ibn Aws ibn al-Hadathan al-Nasri, from Abu Dharr, he said: I heard the Messenger of Allah, peace and blessings of Allah be upon him, saying: "In camels is their Zakat, and in sheep is their Zakat, and in cattle is their Zakat, and in cloth is its Zakat."