Yahya related to me from Ibn Shihab from Salim ibn Abdullah from his father that Umar ibn al-Khattab used to take a twentieth from the cereals and olive oil of the Nabatean christians, intending by that to increase the cargo to Madina. He would take a tenth from pulses.  

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 Malik from Ibn Shihab that as-Sa'ib ibn Yazid said, "As a young man I used to work with Abdullah ibn Utba ibn Masud in the market of Madina in the time of Umar ibn al-Khattab and we used to take a tenth from the Nabateans."  

أَنَّهُ قَالَ كُنْتُ غُلاَمًا عَامِلاً مَعَ عَبْدِ اللَّهِ بْنِ عُتْبَةَ بْنِ مَسْعُودٍ عَلَى سُوقِ الْمَدِينَةِ فِي زَمَانِ عُمَرَ بْنِ الْخَطَّابِ فَكُنَّا نَأْخُذُ مِنَ النَّبَطِ الْعُشْرَ  

Yahya related to me from Malik that he had asked Ibn Shihab why Umar ibn al Khattab used to take a tenth from the Nabateans, and Ibn Shihab replied, "It used to be taken from them in the jahiliyya, and Umar imposed it on them."  

أَنَّهُ سَأَلَ ابْنَ شِهَابٍ عَلَى أَىِّ وَجْهٍ كَانَ يَأْخُذُ عُمَرُ بْنُ الْخَطَّابِ مِنَ النَّبَطِ الْعُشْرَ فَقَالَ ابْنُ شِهَابٍ كَانَ ذَلِكَ يُؤْخَذُ مِنْهُمْ فِي الْجَاهِلِيَّةِ فَأَلْزَمَهُمْ ذَلِكَ عُمَرُ