Hawzah News Agency – The commander of the faithful, Imam Ali peace be upon him says:

المَواعِظُ صَقالُ النُّفوسِ، وجَلاءُ القُلوبِ.

'Exhortations are the polishers of the self and the cleansers of the heart.'

Source: Ghurar al-Hikam, no. 1354