Instructions for an officer sent to collect tax
Nahj al-Balāgha|Volume 1|Book 2|Chapter 26
وَآمَرَهُ أَلَّا يَجْبَهَهُمْ، وَلَا يَعْضَهَهُمْ، وَلَا يَرْغَبَ عَنْهُمْ تَفَضُّلاً بِالْإِمَارَةِ عَلَيْهِمْ، فَإِنَّهُمُ الْإِخْوَانُ فِي الدِّينِ، وَالْأَعْوَانُ عَلَى اسْتِخْرَاجِ الْحُقُوقِ.
He also ordered him that he should not harass them, should not be harsh on them and should not turn away from them because of superiority of official position over them, because they are brethren in faith and help in the recovery of levies.