Musannaf Ibn Abi Shaybah

Hazrat Razeeq narrates that when Hazrat Umar bin Abdul Aziz appointed me as governor, he wrote me a letter stating: "From among the Muslim traders, whoever passes by you with his goods, take one dinar of zakat for every forty dinars, and if it is less than that, then take according to that proportion until it reaches twenty dirhams. And when it becomes less than a third of a dinar, then do not take anything, leave it. And for whatever you have taken from them, write for them a clearance for the year. And if any trader from among the people of dhimma passes by you with goods that are declared and used for trade, then collect one dinar of zakat for every twenty dinars, and if it is less than that, then according to that proportion until it reaches ten dinars. And when it becomes less than a third of a dinar, then leave it, do not collect anything from it. And for them as well, for whatever you have collected, write a clearance for the year."