The Surgeon and the Rabbi
Said the "Yud": "In the same way that a surgeon may shed a man's blood in order to heal his body, a leader may shame a sinner even in public in order to cure his soul. And just as a surgeon may not operate when he knows it will not avail the sick patient, the leader may not shame a sinner when he knows that his rebuke will accomplish no good."
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Source: Tiffereth ha-Yehudi