Delusions will not arise

"The key to cultivating the Way is knowing that your own mind is originally pure, that it is neither created nor destroyed, and that it is free of discrimination. The mind whose nature is perfectly pure is your true teacher and superior to any of the buddhas of the ten directions you might call upon.

And how do you know your mind is originally pure? The shastras say "Within the body of every being is their admantine buddha nature. Like the sun, it fills the world with its perfect light. But because it's covered by the dark clouds of the five Skandhas [Form, Sensation, Perception, Memory and Consciousness], it can't shine forth, like a lamp inside a jar." For example, when the clouds and mists of the world arise in every direction and turn the sky dark, does the sun stop shining? The reason there's no light isn't that the light has been destroyed but that it's been covered up by clouds and mist. The pure mind of every being is like this. It's just obstructed by the dark clouds of attachment, delusion, and affliction. If you can concentrate on guarding the mind, delusions will no longer arise, and the reality of nirvana will spontaneously appear. Thus you should know that your mind is originally pure."

Hongren, the fifth zen patriarch. Discourse on the supreme vehicle.