The Importance of Rebuke

In the synagogue of Radin, a sign hung on the wall: “Anyone who dares to raise his hand against his friend will be placed in cherem!” Once, a notorious bully beat another Jew viciously and the Chofetz Chaim, zt”l, instructed the shamash to punish the offender accordingly. Fearing a reprisal, the shamash conveniently absented himself from shul for the following tefillah.
As soon as the Chofetz Chaim noticed the absence of the shamash, he took matters into his own hands. The gadol ascended the bima himself and declared, “In order to fulfill the mitzvah of ‘fearing no man,’ (Devarim 1:17) I hereby pronounce so-and-so in cherem until he repents and asks forgiveness!”
A few hours later, the bully entered the shul in a contrite frame of mind, admitted his sin before everyone, and publicly begged forgiveness of his victim!
The Chofetz Chaim often directed other Rabbonim to actively rebuke their congregations. He would say, “Picture the heavenly judgment of an average baal habayis. The court will ask him if he set aside time for Torah study, and he will also be asked all the other questions normally put before the deceased. The defendant will offer various excuses but none will be accepted because the heavenly court knows the absolute truth. Finally, the baal habayis will try to exonerate himself by saying that the rav of his community never told him anything was wrong! And this excuse will be accepted to a certain degree because you never rebuked your flock. Why allow the sins of all those people to rest on your shoulders?”