Yahya related to me from Malik that he had asked Ibn Shihab whyUmar ibn al Khattab used to take a tenth from the Nabateans, and IbnShihab replied, "It used to be taken from them in the jahiliyya, andUmar imposed it on them."
USC-MSA web (English) reference: Book 17, Hadith 49
Arabic reference: Book 17, Hadith 625