If it be true that a man is rich who wants nothing, a wise man is a very rich man.
 
[S’il est vrai que l’on soit riche de tout ce dont on n’a pas besoin, un homme fort riche, c’est un homme qui est sage.]

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

The Characters [Les Caractères], ch. 6 “Of Gifts of Fortune [Des Biens de Fortune],” § 49 (6.49) (1688) [tr. Van Laun (1885)]
    (Source)

(Source (French)). Alternate translations:

If he is only rich who wants nothing, a very wise Man is a very rich Man.
[Bullord ed. (1696)]

If a Man is rich, by all which he does not want, a wise Man is a very rich Man.
[Curll ed. (1713)]

If he is rich who wants nothing, a very wise Man is a very rich Man.
[Browne ed. (1752)]

If it is true that wealth consists in having few wants, the wise man is a very wealthy man.
[tr. Stewart (1970)]