Abu ʿAbdillah Muhammad ibn Idris ash-Shafi’ee 204 AH (May Allah have mercy on him) said,

من وعظ أخاه سراً ، فقد نصحه وزانه ومن وعظه علانية ، فقد فضحـه وخانـه

“To admonish your brother in private is to advise him and improve him. But to admonish him publicly is to disgrace and shame him.”

Taken from: Hilyatul Awliyaa 9/140