To be unstained in all environments is called no thought. If you stop thinking of myriad things and cast aside all thoughts, as soon as one instant of thought is cut off, you will be reborn in another realm.

The Dharma of no-thought means even though you see all things, you do not attach to them, but, always keeping your own nature pure, cause the six thieves (the fields of the senses) to exit through the six gates.

Even though you are in the midst of the six dusts, you do not stand apart from them, yet are not stained by them, and are free to come and go.