To found the reward for virtuous actions on the approval of others is to choose too uncertain and shaky a foundation. Especially in an age as corrupt and ignorant as this, the good opinion of the people is a dishonor. Whom can you trust to see what is praiseworthy?
 
[De fonder la recompence des actions vertueuses, sur l’approbation d’autruy, c’est prendre un trop incertain et trouble fondement, signamment en un siecle corrompu et ignorant, comme cettuy cy la bonne estime du peuple est injurieuse. A qui vous fiez vous, de veoir ce qui est louable?]

Michel de Montaigne (1533-1592) French essayist

Essays, Book 3, ch. 2 “Of Repentence [Du Repentir]” (1586) (3.2) (1595) [tr. Frame (1943)]
    (Source)

This essay first appeared in the 1588 ed. The second sentence/phrase (on the age being so corrupt) and following were added for the 1595 ed.

(Source (French)). Alternate translations:

To ground the recompence of vertuous actions, upon the approbation of others, is to undertake a most uncertaine or troubled foundation, namely in an age so corrupt and times so ignorant, as this is: the vulgar peoples good opinion is injurious. Whom trust you in seeing what is commendable?
[tr. Florio (1603)]

To ground the Recompence of virtuous Actions upon the Approbation of others, is too uncertain and unsafe a Foundation; especially in so corrupt and ignorant an Age as this, the good Opinion of the Vulgar is injurious. Upon whom do you relie to shew you what is recommendable?
[tr. Cotton (1686)]

To ground the recompense of virtuous actions upon the approbation of others is too uncertain and unsafe a foundation, especially in so corrupt and ignorant an age as this, wherein the good opinion of the vulgar is injurious: upon whom do you rely to show you what is recommendable?
[tr. Cotton/Hazlitt (1877)]

To base the reward of virtuous actions on the approbation of others is to choose a too uncertain and obscure foundation. Especially in a corrupt and ignorant age like this, the good opinion of the vulgar is offensive; to whom do you trust to perceive what is praiseworthy?
[tr. Ives (1925)]

Basing the recompense of virtuous deeds on another’s approbation is to accept too uncertain and confused a foundation -- especially since in a corrupt and ignorant period like our own to be in good esteem with the masses is an insult: whom would you trust to recognize what was worthy of praise!
[tr. Screech (1987)]