Parshat Acharei Mot begins by talking about the laws of Yom Kipper and slaughtering Korbanot. Then the Torah talks about the Issurei Arayot. The next Parsha talks about being “Kadosh” and community life. Why are these laws listed here? What constitutes Kedusha?
The Kli Yakar says that these commandments are similar to what happened in יתרו after Hashem said that Bnai Yisrael will be holy, “Veotom Tiyhun Li Mamlechet Kohanim Vagoy Kadosh.” Rav Levi says that the Aseret Hadibrot are hinted to in the laws listed in Kedoshim (for a full discussion of this see R. Menachem Leibtag discussion @ www.Tanach.org).
Chazal say that whenever you distance yourself from Averot, you find Kedusha. This is the reason why the Halachot in Kedoshim follow and are followed by Arayot.
In Emor, the Kohen is made Kadosh by being prohibited from marrying a Zona, Chalala, Gerusha, Chalutza, or a Giyoret. The Kli Yakar believes that being Kadosh is not just a status, but it is also a commandment by distancing ourselves from the Arayot.
In all of Sefer Vayikra, there are different levels of Tumah and Kedusha. In Parshat Vayikra, the Torah distinguishes between pure and impure types of Korbanot. In Parshat Shemini, the Torah distinguishes between pure and impure animals. Tazria and Metzora discuss how a Zav, a Metzora, and a woman who gave birth become pure. Parshat Emor talks about how regular Kohanim and Kohanei Gedolim each have their greater status of Kedusha and how they each have extra Issurim.
The laws in Kedoshim about communal life are also “Arayot” to an extent Just as we can not lust after close relatives, so too we should not lust after money and prestige. Just as the first three books of Vayikra separate animals into different categories of Kedusha, those who follow the laws of Kedoshim, Perek 19, are separated and holier from the rest of the world. These people are ethical businessman and judges, respectful of their elders, their parents, and Hashem, are kind to the Zar, Cheresh, and Iver, do not avenge fellow Jews, do not bare grudges, and love fellow Jews. Unfortunately, although many Jews keep major Halachot like Shabbat, Kosher, and worshipping Hashem, these same Jews speak Lashon Hara, hate other Jews, and act wrongly in business life. A pious Jew must keep every Mitzva in the Torah.