You can tell the man who rings true from the man who rings false, not by his deeds alone, but also by his desires.

[Δόκιμος ἀνὴρ καὶ ἀδόκιμος οὐκ ἐξ ὧν πράσσει μόνον, ἀλλὰ καὶ ἐξ ὧν βούλεται.]

Democritus (c. 460 BC - c. 370 BC) Greek philosopher
Frag. 68 (Diels) [tr. Bakewell (1907)]
    (Source)

Diels citation "68. (40 N.) DEMOKRATES. 33." Bakewell lists this under "The Golden Sayings of Democritus." Freeman notes this as one of the Gnômae, from a collection called "Maxims of Democratês," but because Stobaeus quotes many of these as "Maxims of Democritus," they are generally attributed to the latter.

Alternate translations:

• "A man is approved or rejected not only by what he doth, but by what he wills." [Hammond (1845)]
• "The worthy and the unworthy man are to be known not only by their actions, but also their wishes." [tr. Freeman (1948)]
• "One of esteem and one without it do not only act for different reasons but they desire for different reasons too." [tr. @sententiq (2018), fr. 67]
• "Accomplished or unaccomplished we shall call a man not only from what he does but from what he desires, too." [Source]
• "The worthy and unworthy are known not only by their deeds, but also by their desires." [Source]