Hassidout sur Les Proverbes 9:8

Speak to Aharon your brother - we see to explain that [here] the Holy Torah is teaching people who rebuke others that they should not rebuke those who are clowns and empty-headed, into whom clearly the words [of rebuke] will not enter into their ears at all, as it is said "do not rebuke a scoffer" (Prov. 9:8); only people who pay attention to the voice of rebuke and mussar and who want to do teshuvah, to those one speak and directs to the ways of teshuvah.