Excerpts taken from Tzvi Fishman's Blog
This week's Torah portion is "Kedoshim."
"Hashem spoke to Moshe saying, Speak to the entire assembly of the Children of Israel and say to them: You shall be holy, for I, Hashem your G-d, am holy."
Rashi states: "You shall be holy by being removed from sexual transgression and from sin, for wherever you find a restriction from sexual immorality, you find holiness."
Every Jew is holy by nature of his or her holy Jewish soul. However, sins, especially sexual transgression, pollute a Jew's intrinsic holiness in the same manner that garbage pollutes a stream. Through t'shuva (repentance) a person can remove the garbage from the stream, but without t'shuva, the pure Jewish soul remains stained.
The Ramban takes Rashi's explanation one step further by adding that a Jew does not only have to stay away from major sexual transgressions. Rather, when the Torah commands us to "be holy," it is telling us that we have to sanctify our behavior even in permitted matters, like the relations between a man and his wife. (Ramban on the Torah, "Kedoshim," 19:1). For instance, while a man is allowed to have relations with his wife during the permitted periods, our Sages warn us not to be like roosters with our mates (i.e. not to over do it). Being holy also means that a Jew is not supposed to gaze lustfully at women, whether in the street, at the movies, on TV, or on the Internet.
This vital subject is the very foundation of Jewish life. Jewishness is not just a religion, or national identity. Jewishness is a call to live holy lives as individuals and as a holy nation. The commandments of the Torah are our ladder of sanctification, and, as Rashi and the Ramban explain, the first rung is holiness in our sexual lives.