坐禪三昧經 2.73

2.73

無明緣行。云何名行？行有三種：身行、口行、意行。云何身行？入息出息是身行法。所以者何？是法屬身，故名身行。

Ignorance conditions formations. What are called formations? There are three kinds of formations: bodily formations, verbal formations, and mental formations. What are bodily formations? Inhalation and exhalation are the dharmas of bodily formations. Why is this? Because these dharmas belong to the body, they are called bodily formations.