Abdullah bin Abi Bakr bin Muhammad bin Amr bin Hazm (may Allah have mercy on him) said that a letter came to my father from Umar bin Abd al-Aziz (may Allah have mercy on him) while he was at Mina, saying: Do not collect zakah from horses or from honey.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الزكاة / 7416