Gautam Buddha was going to a Village to give sermon with Ananda (chief disciple of Buddha).
They crossed a small canal and went further towards the village. It was a Hot day and sun was bright. After some time Buddha felt thirsty and sat down under a tree.
Buddha asked Ananda to fetch water from the canal they had just crossed. In mean time a Bullock cart had crossed the canal and water had become dirty. When Ananda reached the canal, he found water is unfit for drinking. He came back and told buddha that water is not clean.
But Buddha insisted and said go back and wait till water becomes clean again. By the time Ananda had reached back to the canal, some mud had already settled down, but water was still unfit for drinking.Nothing else to do Ananda sat silently near the canal and started meditating.
After few minutes he opened eyes to see water and to his surprise water was clean. Mud had settled down on its own. Same is the nature of our mind also. Our thoughts are like Mud which pollutes our consciousness. Moment we stop paying attention to thoughts, stop cooperating with them, stop analyzing thoughts, stop bothering with them, silence starts descending on us. and we regain our pure consciousness state.