釋禪波羅蜜次第法門 7.58

7.58

復次，短中覺長則定細，長中知短則是麁。何故爾？如息從鼻至胸則盡，此行處雖短，而時若大，久久方至，臍。此則行處短而時節長也。若就此而論，短中覺長則定細。覺長中而短是麁者，如心麁故，息從鼻至臍，道里極長，而時節短，欻然之間，即出至鼻。何以故？心麁氣息行疾故。此雖長而短，然此息短則是心麁也，故云短中長而細，長中短而麁也。如此覺長短時節，知無常由心，生滅不定故。今息長短相貌非一，得此定時，覺悟無常，轉更分明。證欲界定，故名亦愛；觀行覺無常，故名亦策。此略說第三、知息長短，破欲界定也。

Furthermore, perceiving length within shortness, the absorption is subtle; knowing shortness within length, it is coarse. Why is this? For example, the breath is exhausted from the nose to the chest: although the path traveled is short, the time is long, taking a great while before reaching the navel. This means that the path traveled is short while the duration is long. If evaluated according to this, perceiving length within shortness means the absorption is subtle. As for perceiving shortness within length being coarse: because the mind is coarse, the breath goes from the nose to the navel, the route being extremely long, yet the duration is short, abruptly exiting out to the nose. Why is this? Because the mind is coarse, the breath moves swiftly. Although long, it is short; but this breath's being short is precisely because the mind is coarse. Therefore it is said that length within shortness is subtle, while shortness within length is coarse. In this way, perceiving the duration of long and short, one knows that impermanence arises from the mind, with arising and ceasing being unstable. Now, the characteristics of the length and shortness of the breath are multiple; upon attaining this absorption, the awakening to impermanence becomes even clearer. Realizing the desire-realm absorption is therefore called 'also [possessing] craving'; reflective contemplation awakening to impermanence is therefore called 'also [possessing] spurring.' This briefly explains the third, knowing whether the breath is long or short, which destroys the desire-realm absorption.