Maulana Wahiduddin Khan | The Sunday Guardian | August 7, 2016, p. 12
A milkman, deeply influenced by Gautam Buddha insisted that the Buddha visit him and share his nuggets of wisdom. In lieu of this, the milkman offered to present milk to the Buddha. He agreed. When the Buddha set out to visit the milkman he took with him a container in which he intentionally put some mud.
The milkman took the container but just as he was about to pour milk into it, he realized that the container had impurity. The milkman cleansed the container, removed all the impurities and then poured milk into it. He then presented the contained to the Buddha. Upon getting the container, the Buddha rose to leave. Surprised, the milkman asked the Buddha why was he leaving before imparting wisdom. The Buddha replied that he just did that. Unable to comprehend it, the milkman urged the Buddha to explain the learning to him.
The Buddha told the milkman that our heart is similar to the container and the thoughts that preoccupy us are like impurities in the container. In order to attain wisdom, we must purify our mind and make it free of all impure thoughts. The Buddha asked the milkman to cleanse himself of his impure thoughts for only then would he be able to imbibe any further learning.
What is this impurity? It is nothing but negative thinking. When a person lives in a society, he repeatedly undergoes unwanted experiences that arouse negative thought. These negative thoughts bring about all kinds of evil such as hatred, malice, dishonesty, revenge and finally violence. A person whose mind is filled with negative emotions is like a polluted container. Such a person cannot draw divine inspiration. Inspiration comes only to a purified soul. One who is not a purified soul would remain devoid of divine inspiration.