瑜伽論記 10.170

10.170

景云：有所遮防故名為戒，戒通善惡，善惡各有遮防，今明善戒遮防惡法所以名戒，若言防非止惡故名戒者，惡戒云何得名防非止惡，由有此妨故得言遮防名戒亦名律儀，內調名律外現法式名律儀律儀雖通善惡戒今明善律儀也。

Jing says: "Because it has the function of barring and preventing, it is called a precept. Precepts apply to both good and evil, each having what it bars and prevents. Here, clarifying the good precepts, they bar and prevent evil dharmas, and are therefore called precepts. If one were to say that 'preventing wrongs and stopping evil' is the reason it is called a precept, how could an evil precept be called 'preventing wrongs and stopping evil'? Due to this difficulty, one can say that barring and preventing is called a precept and is also called disciplined conduct. Internal regulation is called discipline, and external manifestation of rules is called disciplined conduct. Although disciplined conduct applies to both good and evil precepts, here it is the good disciplined conduct that is clarified."