Usbek to Rhedi in Venice
If there is a God, my dear Rhedi, he must necessarily be just ; for if he were not, he would be the worst and most imperfect of all beings.
Justice is a relationship of agreement that really exists between two things ; this relationship is always the same, whatever being considers it, whether it be God, whether it be an angel, or whether indeed it be a man.
It is true that men do not always see these relationships ; often, even when they see them, they depart from them, and their own interest is always what they see best. Justice raises its voice, but has trouble making itself heard in the tumult of the passions.
Men can commit injustices because they have an interest in committing them and would rather satisfy themselves than others. It is always by a reflection on themselves that they act ; no one is gratuitously bad : there must be a reason that determines him, and this reason is always a reason of interest. 
But it is not possible for God ever to do anything unjust : once we suppose that he sees justice, he must necessarily follow it ; for as he has need of nothing, and suffices to himself, he would be the most evil of all beings, since he would have no interest in being evil.
Thus, if there were no God, we still ought to love justice, that is, try our best to be like that being of which we have such an excellent notion, and who, if he existed, would necessarily be just. Free as we would be from the yoke of religion, we ought not to be free of that of equity.
This, Rhedi, is what has made me think that justice is eternal, and not dependent on human conventions ; and were it dependent on them, that would be a terrible truth that one would have to conceal from oneself.
We are surrounded by men stronger than ourselves ; they can harm us in a thousand different ways ; three-quarters of the time, they can do so with impunity. What relief for us to know that there is an inner principle in the heart of all those men that fights in our favor and shelters us from their undertakings !
Otherwise we would have to be in continual alarm ; we would pass before men as before lions, and would never be assured for a moment of our lives, our possessions, nor our honor.
All these thoughts provoke me against those doctors who represent God as a being who makes a tyrannical exercise of his power,  who make him act in a manner in which we ourselves would not want to act, for fear of offending him ; who accuse him of all the imperfections he punishes in us, and in their contradictory opinions represent him sometimes as an bad being, and sometimes as a being who hates evil, and punishes it.
When a man examines himself, what satisfaction for him to find that his heart is just ! This pleasure, severe as it is, should delight him : he sees his being as far above those whose heart is not, as he sees himself above tigers and bears. Yes, Rhedi, if I were sure of always following inviolably this equity which I have before my eyes, I would deem myself the first among men.
Paris this 1st day of the moon of Gemmadi I, 1715