A slave has but one master; an ambitious man has as many masters as there are people who may be useful in bettering his position.

[L’esclave n’a qu’un maître; l’ambitieux en a autant qu’il y a de gens utiles à sa fortune.]

Jean de La Bruyère (1645-1696) French essayist, moralist

The Characters [Les Caractères], ch. 8 “Of the Court [De la Cour],” § 70 (8.70) (1688) [tr. Van Laun (1885)]
    (Source)

(Source (French)). Alternate translations:

A Slave has but one Master, an ambitious Man a great many, all those who are useful to him in making his fortune.
[Bullord ed. (1696)]

A Slave has but one Master; an ambitious Man has as many as there are People useful to him in making his Fortune.
[Curll ed. (1713)]

A purchased Slave has but one Master: An ambitious Man must be a Slave to all who may conduce to his Aggrandizement.
[Browne ed. (1752)]

A slave has only one master; an ambitious man is enslaved to all those who may help to further his advancement.
[tr. Stewart (1970)]