حَدَّثَنِي يَحْيَى، عَنْ مَالِكٍ، عَنِ ابْنِ شِهَابٍ، عَنْ سَالِمِ بْنِ عَبْدِ اللَّهِ، عَنْ أَبِيهِ، أَنَّ عُمَرَ بْنَ الْخَطَّابِ، كَانَ يَأْخُذُ مِنَ النَّبَطِ مِنَ الْحِنْطَةِ وَالزَّيْتِ نِصْفَ الْعُشْرِ يُرِيدُ بِذَلِكَ أَنْ يَكْثُرَ الْحَمْلُ إِلَى الْمَدِينَةِ وَيَأْخُذُ مِنَ الْقُطْنِيَّةِ الْعُشْرَ ‏.‏

Yahya related to me from Ibn Shihab from Salim ibn Abdullah fromhis father that Umar ibn al-Khattab used to take a twentieth from thecereals and olive oil of the Nabatean christians, intending by that toincrease the cargo to Madina. He would take a tenth from pulses. Translation Not Available

Book Ref: Muwatta Imam Malik Book 17 Hadith 623
Web Ref:  Muwatta Imam Malik Book 17 Hadith 47