Provided by CLAL: The National Jewish Center for Learning and Leadership, a multi-denominational think tank and resource center.
Where does the command "You shall be holy," the defining moment of this portion, fit in? Is it the conclusion, the underlying teleology of chapter 18’s prescriptions against forbidden sexual practices? Or is it the introduction, the topic sentence, of the compact code of laws that forms chapter 19?
According to Ramban, Rabbi Moses ben Nachman (1194-1270), both of the above possibilities minimize the centrality and significance of holiness in God’s plan for human conduct. As a result, both possibilities miss the point. For Ramban, holiness is the key to the fulfillment of the entire Torah; rather than standing alone, it must inform and illuminate the performance of each and every commandment.
Without the all-encompassing prescription to be "wholly holy," Ramban envisions the disturbing possibility of the "scoundrel with Torah license," a cosmically annoying individual who mechanically fulfills all of the specific rules of the Torah and refrains from all the specific prohibitions. While this individual fulfills the specifics of the Torah, the Torah does not animate or fill out this scoundrel’s personality. Rather, the scoundrel operates crudely, selfishly, opportunistically in areas and moments in which specific Torah law is silent.
The Command to Holiness
In Ramban’s view, the command to holiness, to aspire constantly toward a divinely inspired sanctification, makes the possibility of the scoundrel obsolete. The generalized divine command to be holy not only informs each specific command, but fills in the gaps of silences between commanded moments.
In the Torah, God speaks to us in a dual language–stereo, if you will–specific commands in tandem with a general, informing and defining charge or exhortation. Ideal human conduct is approached when we hear, at all times, both a detailed, specific command and an accompanying whisper, "Be holy." Holiness is achieved through our committed and sustained response not only to the specific instructions, but to the generalized instruction as well.
For Ramban, holiness, then, is the defining, shining moment not only of this portion, but of every fully realized human action.