Maliks Muwatta Book 017, Hadith Number 003.

Section : Things on which Zakat must be Paid.

Yahya related to me from Malik that he had heard that Umar ibn Abd al-Aziz wrote to his governor in Damascus about zakat saying, "Zakat is paid on the produce of ploughed land, on gold and silver, and on livestock."

Malik said, "Zakat is only paid on three things| the produce of ploughed land, gold and silver, and livestock."