Shobogenzo Zuimonki

Book 2

2-13

Dogen also said,

Even according to secular morality, when changing clothes, sitting, or lying down in places where no one can see you, or in a dark room, failing to hide what should be hidden, having no propriety is criticized as being shameless before the devas and demons. You should hide what should be hidden, and be discreet about that which requires discretion just as if someone were watching.

In the buddha-dharma, the precepts speak of the same attitude. Therefore as a practitioner of the Way, (you should) keep the Buddha’s precepts in mind, refraining from committing evil even though no one might see you or notice (what you do); do not discriminate between inside or outside or between bright or dark.