坐禪三昧經 1.80

1.80

觀棄捨亦念息入出，諸染愛煩惱身心五陰諸有為法棄捨，是第一安隱。如是觀是名隨法意止觀，是名十六分。

When contemplating relinquishment, one also is mindful of breathing in and out: relinquishing all kleśas of tainted craving, physical body and mind, the five aggregates, and all conditioned dharmas is the foremost tranquility and security. Contemplating in this way is called contemplation in conformity with mindfulness of dharmas. These are called the sixteen parts.