Ruzayq bin Hayyan said: Sayyiduna Umar bin Abd al-Aziz (may Allah have mercy on him) wrote to me that I should collect from the dhimmi traders a twentieth of those goods, and if it is less, then in the same proportion, until it comes down to ten dinars. If it falls short by a third of a dinar, then collect nothing, and whatever you collect, record it in writing for the year.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجزية / 18775