It has eternally been observed that any man who has power is led to abuse it; he continues until he finds limits.

[C’est une expérience éternelle, que tout homme qui a du pouvoir est porté à en abuser; il va jusqu’à ce qu’il trouve des limites.]

Charles-Lewis de Secondat, Baron de Montesquieu (1689-1755) French political philosopher

Spirit of Laws [The Spirit of the Laws; De l’esprit des lois], Book 11, ch. 4 (11.4) (1748) [tr. Cohler/Miller/Stone (1989)]
    (Source)

See Acton (1887).

(Source (French)). Other translations:

Constant experience shows us, that every man invested with power is apt to abuse it; he pushes on till he comes to the utmost limit.
[tr. Nugent (1750)]

Timeless experience tells us that any man who holds power is inclined to abuse it : he continues until he encounters limits.
[tr. Stewart (2018)]