The devotional aspect of vinaya practice lies in taking refuge in and relying on the Three Jewels, namely the Buddha, the Dharma, and the Sangha. On the other hand, the practical aspect of vinaya practice, where it ceases to be merely personal but begins to shape one's interaction with others, is the keeping of the five precepts: no killing, no stealing, no sexual misconduct, no verbal misconduct, and no using intoxicants. The five precepts are the simplest codification of precepts in Buddhism, yet they are the foundation upon which all the other systems of Buddhist precepts and vows rest. No matter which set of precepts we consider, including the exhaustively detailed monastic code, not one of them falls outside the scope of the five precepts. Not one of the various codes of conduct that have evolved over Buddhism's long history omits the five precepts. It is no exaggeration to say that the five precepts are the most important precepts in Buddhism.
At first sight, some might assume that the five precepts are easy to keep because they appear to be so simple. One might be tempted to assume that they merely comprise a sort of universal code of acceptable, civilized behavior. Such an assumption is, however, quite superficial. After committing ourselves to keeping and integrating the five precepts into our lives, we soon come to realize that they are not as easily kept as we might have thought. By living with the precepts and by engaging in continued analysis and scrupulous study of both the precepts and ourselves, we will begin to penetrate them more deeply, and realize that they are in fact extremely subtle. It is through applying ourselves as best we can to the practice of the precepts that we come to understand their significance, and the profound influence they exert on us and on our relationships with others.
As we noted before, all of the different systems of precepts branch out from this fundamental code, so if a practitioner cannot seriously commit to the practice of the five precepts, it will be extremely difficult for him or her to practice any of the other, more detailed, systems. Conversely, a practitioner who can observe the five precepts in the smallest detail would be said to be very close to attaining a pure buddha land. For this reason, all practitioners who wish to take the bodhisattva precepts should pay special attention to the observance of the five precepts. We should not be casual about keeping the precepts and integrating them into our daily lives in the mistaken belief that they are simple and obvious. If we approach this practice haphazardly, we deprive ourselves of the opportunity to appreciate the many subtleties in the meaning and function of the five precepts, and may never truly experience the dignity and profound insight that keeping these precepts affords.
Source : "The Bodhisattva Precepts"