四分比丘戒本疏 2.146

2.146

第七釋迦佛略。此佛世人性多煩惱，放逸不修，設修少善便生喜足，又多惡業。為對治彼，故制戒云「善護於口言」者，他詰罪時莫惡言報也。又善護於口言者，若自發言，離四過也。「自淨其志意」者，斷諸煩惱，修不放逸，樂修多善也。「身莫作諸惡」者，離身過也。意能發業，故居中間，表上發語，表下發身也。「此三業道淨」者，證涅槃時是最淨處。故次文云「能得如是行，是大仙人道」也。

Seventh is the abbreviated [prātimokṣa] of Śākyamuni Buddha. The nature of the people of this Buddha's era has many afflictions; they are heedless and do not cultivate, and if they cultivate a little wholesome deed they readily become complacent, and they also commit much bad karma. To counteract that, he therefore instituted the precept, saying, "Guarding well the words of one's mouth," meaning that when others question one's offences, one does not retort with harsh words. Furthermore, "guarding well the words of one's mouth" means that when speaking oneself, one abandons the four faults. "Purifying one's own mind and intention" means severing all afflictions, cultivating heedfulness, and taking pleasure in cultivating many wholesome deeds. "Let the body commit no evils" means abandoning bodily faults. Because the mind can initiate karma, it stands in the middle, indicating the initiation of speech above and the initiation of bodily actions below. "Purity in these three karmic paths" refers to the most pure place when realizing nirvāṇa. Therefore, the subsequent text states, "To be able to attain such practice is the path of the Great Sage."