Aristotle,
Politics
(4th century BC)
“ The idea of a king is to be a protector of the rich against unjust treatment, of the people against insult and oppression. Whereas a tyrant, as has often been repeated, has no regard to any public interest, except as conducive to his private ends; his aim is pleasure, the aim of a king, honor. Wherefore also in their desires they differ; the tyrant is desirous of riches, the king, of what brings honor. And the guards of a king are citizens, but of a tyrant mercenaries. That tyranny has all the vices both of democracy and oligarchy is evident. As of oligarchy so of tyranny, the end is wealth ”

