Men who want to be feared must necessarily fear the very people who fear them.

[Etenim qui se metui volent, a quibus metuentur, eosdem metuant ipsi necesse est.]

Marcus Tullius Cicero (106-43 BC) Roman orator, statesman, philosopher

De Officiis [On Duties; On Moral Duty; The Offices], Book 2, ch. 7 (2.7) / sec. 24 (44 BC) [tr. Edinger (1974)]
    (Source)

(Source (Latin)). Alternate translations:

For those who desire to have others be afraid of them, must needs be afraid of those others in their turns.
[tr. Cockman (1699)]

For they who desire to become objects of terror to others, must dread those who regard them with fear.
[tr. McCartney (1798)]

For it is a necessary consequence, that men fear those very persons by whom they wish to be feared.
[tr. Edmonds (1865)]

For it is inevitable that those who wish to be feared should themselves fear the very persons by whom they are feared.
[tr. Peabody (1883)]

For men involuntarily fear those whom they intimidate.
[tr. Gardiner (1899)]

Those who wish to be feared must inevitably be afraid of those whom they intimidate.
[tr. Miller (1913)]