Abdul Hamid, H. bin, A. F. Abdul Hamid, and A. Abdul Wahab. “Development of Zakat Collection During Caliph Umar Al-Khattab”. Al-Muqaddimah: Online Journal of Islamic History and Civilization, vol. 6, no. 1, Jan. 2019, pp. 28-42, https://vmis.um.edu.my/index.php/MUQADDIMAH/article/view/15708.