The Buddha said that sometimes there is ... - Dhamma by Ajahn Jayasāro
The Buddha said that sometimes there is the sound of thunder in the sky, but no rain falls. This is like the case of someone who has read a lot and can speak convincingly on the Dhamma, but has no true insight into the Four Noble Truths. Some people, on the other hand, have gained insight into the Four Noble Truths, but have read little and cannot speak well. Sometimes there is no thunder, but rain falls and refreshes the parched earth. We can learn whether a teacher is trustworthy, not by how self-confident and articulate they appear, but by the extent to which they show a consistent freedom from greed, hatred and delusion
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