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." (IT)
USC-MSA web (English) reference: Book 17, Hadith 49 (IT)
Arabic reference (IT): Book 17, Hadith 625 (IT)