Imam Malik (may Allah have mercy on him) asked Ibn Shihab (may Allah have mercy on him): On what basis did Sayyiduna Umar (may Allah be pleased with him) collect a tenth from the Nabat region? He said: It used to be collected from them in the Era of Ignorance (Jahiliyyah), so Sayyiduna Umar (may Allah be pleased with him) kept it in place.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجزية / 18768