Al-Kāfi - Volume 1 > Chapter on Utilization of Knowledge
Hadith #3

3ـ عِدَّةٌ مِنْ أَصْحَابِنَا عَنْ أَحْمَدَ بْنِ مُحَمَّدِ بْنِ خَالِدٍ عَنْ عَلِيِّ بْنِ مُحَمَّدٍ الْقَاسَانِيِّ عَمَّنْ ذَكَرَهُ عَنْ عَبْدِ الله بْنِ الْقَاسِمِ الْجَعْفَرِيِّ عَنْ أَبِي عَبْدِ الله (عَلَيْهِ السَّلام) قَالَ إِنَّ الْعَالِمَ إِذَا لَمْ يَعْمَلْ بِعِلْمِهِ زَلَّتْ مَوْعِظَتُهُ عَنِ الْقُلُوبِ كَمَا يَزِلُّ الْمَطَرُ عَنِ الصَّفَا.

3. A number of our people has narrated from Ahmad ibn Muhammad ibn Khalid from Ali ibn Muhammad al-Qasani from one he mentioned from ‘Abdallah ibn Qasim al-Ja’fari from abu ‘Abdallah (a.s.) who has said the following. “If a scholar preaches and does not practice his words bounce away from the hearts of the audience like rains that bounce away off the rocks.”