From the servant of Allah `Ali, Amir al-mu'minin to the tax collectors:
So now, he who does not fear where he is going, does not send forward for himself that which could protect him. You should know that the obligations laid on you are few, while their reward is much. Even if there had been no fear of punishment for revolt and disobedience, which Allah has prohibited, the reward in keeping aloof from it would be enough (incentive) to abstain from going after it. Behave yourselves justly with the people and act with endurance with regard to their needs, because you are the treasurers of the people, representatives of the community and the ambassadors of the Imams.
Do not deprive anyone of his needs and do not prevent him from (securing) his requirements.For the collection of tax (kharaj) from the people do not sell their winter or summer clothes, nor cattle with which they work, nor slaves. Do not whip anyone for the sake of one Dirham. Do not touch the property of any person whether he be one who prays (a Muslim) or a protected unbeliever, unless you find a horse or weapons used for attack against Muslims, because it is not proper for the Muslims to leave these things in the hands of the enemies of Islam to enable them to have power over Islam.
Do not deny good counsel to yourself, good behaviour to the army, succour to the subjects and strength to the religion of Allah. Strive in the way of Allah as is obligatory on you, because Allah the Glorified, desires us and you to be thankful to Him as best as we can and that we should help Him to the best of our power. And there is no power save with Allah, the All-high, the All- glorious.