Agis and Cleomenes

Ye cannot have the same man as your ruler and your slave. Since in this case also one certainly can apply the fable of the serpent whose tail rebelled against its head and demanded the right to lead in turn instead of always following; so it took the lead, and by the folly of its progress got itself into mischief and lacerated the head, which was compelled, contrary to nature, to follow a part that had neither eyes nor ears.