Hawzah News Agency – Imam al-Askari peace be upon him says:

مَن وَعَظَ أخاهُ سِرّاً فَقَد زانَهُ، ومَن وَعَظَهُ عَلانِيَةً فَقَد شانَهُ.

'He who exhorts his brother in secret has indeed adorned him, and he who exhorts him in public has dishonoured him.'

Source: Tuhaf al-Uqul, no. 489