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

إنّ العالِمَ إذا لم يَعمَلْ بعِلمِهِ زَلَّت مَوعِظَتُهُ عنِ القُلوبِ كَما يَزِلُّ المَطَرُ عنِ الصَّفا.

'When the knowledgeable man does not act upon his knowledge, his exhortation slips away from the hearts like the rain slips off a flat rock.'

Source: Munyat al-Murid, p. 146,181