釋禪波羅蜜次第法門 7.51

7.51

Furthermore, knowing length of time: the inhalation is short, and the exhalation is long. Why is this? Since the in-breath enters swiftly, it is easily exhausted, and thus short; since the out-breath exits sluggishly, it is difficult to exhaust, and thus long. One must also become aware and know that because of inhalation and exhalation, all sufferings and afflictions exist, with coming and going in birth and death, revolving incessantly, such that the mind feels alarm and dread. When the practitioner follows the breath, he knows that the breath possesses various characteristics such as these that are not solitary; therefore it is said that he knows the inhalation and exhalation of the breath.