Kindness consists in part, perhaps, in esteeming and loving people more than they deserve; but then there is a measure of prudence in believing that people are not always equal to what they are taken for.
 
[Une partie de la bonté consiste peut-être à estimer et à aimer les gens plus qu’ils ne le méritent; mais alors une partie de la prudence est de croire que les gens ne valent pas toujours ce qu’on les prise.]

Joseph Joubert (1754-1824) French moralist, philosopher, essayist, poet

Pensées [Thoughts], ch. 5 “Des Passions et des Affections de l’Âme [On the Soul],” ¶ 66 (1850 ed.) [tr. Attwell (1896), ¶ 71]
    (Source)

(Source (French)). Alternate translation:

A part of goodness consists, perhaps, in esteeming and loving people more than they deserve; but then a part of prudence is to believe that people are not always worth what we rate them at.
[tr. Calvert (1866), ch. 5]

Commonly truncated and paraphrased as:

A part of kindness consists in loving people more than they deserve.
[E.g. (1935)]

(Sometimes the "A part of" is left off as well.)