The Republic by Plato Part 1 Page 55

Because you fancy that the shepherd or neatherd fattens or tends the sheep or oxen with a view to their own good and not to the good of himself or his master; and you further imagine that the rulers of states, if they are true rulers, never think of their subjects as sheep, and that they are not studying their own advantage day and night. Oh, no; and so entirely astray are you in your ideas about the just and unjust as not even to know that justice and the just are in reality another’s good; that is to say, the interest of the ruler and stronger, and the loss of the subject and servant; and injustice the opposite; for the unjust is lord over the truly simple and just: he is the stronger, and his subjects do what is for his interest, and minister to his happiness, which is very far from being their own.