וָאַבְדִּל אֶתְכֶם מִן הָעַמִּים לִהְיוֹת לִי
Chapters 18-20 of Sefer Vayikra form one unit dealing with two very distinct subjects in three separate parts . Chapter 18 discusses the laws of forbidden sexual relationships, chapter 19 discusses a variety of laws related to Kedushah, and chapter 20 discusses both themes together. Through this unity, Rashi reasons that the definition of Kedushah is separation from inappropriate sexual relations, a definition which fits clearly with the following juxtaposition:
You shall be holy: Separate (Root: פרש) yourselves from sexual immorality and from sin, for wherever one finds a barrier against sexual immorality, one finds holiness, [for example:], “[They (the kohanim) shall not take in marriage] a woman who is a prostitute or one who was profaned…I, the Lord, Who sanctifies you [am holy]” (Lev. 21:7-8); and, “he shall not profane his offspring…I am the Lord, Who sanctifies him” (Lev. 21:15); and, “They shall be holy…[They shall not take in marriage] a woman who is a prostitute or one who was profaned” (Lev. 21:6-7).
However, a close study of the text involved demonstrates that this is just the beginning of a much larger picture.
There are many ways of determining the topic and unity of a passage in Tanakh. One of the key methods is through the use of keywords, words that are repeated several times. In chapters 18-21 we find four keywords, namely “laws” (root: חק), “rules” (root: שפט), “keep” (root: שמר), and “holy” (root: קדש). “Laws,” “Rules,” and “Holy” all show up ten times while “Keep” appears seven times, both numbers of biblical import, which highlights the thematic role of each of these ideas.
Another method of determining thematic importance is through parallels at the beginning and end of a unit, such a the parallel between 18:3-5 and 20:22-23:
3 You shall not copy the practices of the land of Egypt where you dwelt, or of the land of Canaan to which I am taking you; nor shall you follow their laws. 4 My rules alone shall you observe, and faithfully follow My laws: I the Lord am your God. 5 You shall keep My laws and My rules, by the pursuit of which man shall live: I am the Lord.
22 You shall faithfully observe all My laws and all My regulations, lest the land to which I bring you to settle in spew you out. 23 You shall not follow the practices of the nation that I am driving out before you. For it is because they did all these things that I abhorred them.
This parallel denotes the beginning and end of the section while also reinforcing the topic ideas of Laws and Rules. What is not seen to be a topic, however, is separation from sexual impropriety. Yet it is undeniably a large part of the passage. So what then can be said of the definition of Kedushah from this context?
While Separation (פרישות) is not found in this section at all, and certainly not attached to Kedushah, there is a very similar word that is used here in context of Kedushah. Vayikra 20:24-26 discusses the idea that Israel is “set apart” (root: בדל).
24 and said to you: You shall possess their land, for I will give it to you to possess, a land flowing with milk and honey. I the Lord am your God who has set you apart from other peoples. 25 So you shall set apart the clean beast from the unclean, the unclean bird from the clean. You shall not draw abomination upon yourselves through beast or bird or anything with which the ground is alive, which I have set apart for you to treat as unclean. 26 You shall be holy to Me, for I the Lord am holy, and I have set you apart from other peoples to be Mine.
Thus Kedushah is not simply about Separation, but about being distinguished and set apart.
A perfect demonstration of this is found in the law of shaatnez, found in Vayikra 19:19:
“You shall observe My laws. You shall not let your cattle mate with a different kind; you shall not sow your field with two kinds of seed; you shall not put on cloth from a mixture of two kinds of material.”
This law is generally interpreted as a symbolic law meant to teach man about the importance of separating between distinct realms. It is often taken as being directed against disorder or intermarriage. However, the assumption that shaatnez is inherently problematic, if only on a symbolic level, is hard to maintain once one takes a look at the broader context of the Torah. Due to the fact that shaatnez is only ever mentioned by name in regards to the prohibition of wearing it, many people miss its earlier appearances in the torah. It appears in Sefer Shemot, in 26:1, “As for the Tabernacle, make it of ten strips of cloth; make these of fine twisted linen, of blue, purple, and crimson yarns, with a design of cherubim worked into them,” 26:31, “You shall make a curtain of blue, purple, and crimson yarns, and fine twisted linen; it shall have a design of cherubim worked into it,” 28:6, “They shall make the ephod of gold, of blue, purple, and crimson yarns, and of fine twisted linen, worked into designs.,” 28:15, “You shall make a breastpiece of decision/ worked into a design; make it in the style of the ephod: make it of gold, of blue, purple, and crimson yarns, and of fine twisted linen,” and 39:29, “and sashes of fine twisted linen, blue, purple, and crimson yarns, done in embroidery- as the Lord had commanded Moses,” among others. These verses all refer to the materials of the Mishkan and the garments of the Kohanim. All are composed of linen and colored wool. Thus while shaatnez is forbidden to the average member of Bnei Yisrael, it is in fact mandatory for the Kohanim, and therefore it cannot be inherently bad. Furthermore, even for a normal citizen of Israel it is not entirely forbidden. Bamidbar 15:39, part of the original commandment regarding tzitzit, says that shaatnez is part of tzitzit. “Speak to the Israelite people and instruct them to make for themselves fringes on the corners of their garments throughout the ages; let them attach a cord of blue to the fringe at each corner.” As with the colored wool of the Mishkan and the priestly garments, the colored string of the tzitzit is made of wool. The inclusion of shaatnez, along with the otherwise priestly blue, is part of how tzitzit remind the wearer of their priestly purpose.
The commandment of shaatnez is not itself about two things that need to be kept separate, but about differentiating between two groups with different purposes, the Kohanim and the rest of Bnei Yisrael. Only in tzitzit, the mitzvah intended to remind Bnei Yisrael of their purpose as a “Kingdom of Priests and a Holy Nation” do they wear shaatnez. This is the integral message of the entire section, of Vayikra 18-21. The two ideas of this pericope, that of keeping the Laws/Rules of ‘א as opposed to the Laws of the Nations and that of Kedushah, are actually one. What makes Israel holy is that it is differentiated, and differentiates itself, from the other nations by its practices. However, much like shaatnez, it is not that either set of practices is necessarily good or bad. While the Torah clearly takes a negative stance towards those practices of the nations mentioned in Vayikra 18-21, what is important about them is not their moral quality, but that they are not the practices which ‘א has laid down for Israel to follow. Kedushah is about the fulfilment of purpose, on both the national and individual levels. It’s not just avoiding negative or foreign practices, but also the active fulfillment of the purpose and laws that ‘א laid down for Israel that makes Bnei Yisrael a “Kingdom of Priests and a Holy Nation.”
 Found in his comment on Vayikra 19:2.
 Translation of Rashi from Chabad.org.
 The root שמר also appears in the word “משמרתי” in 18:30, but this is grammatically different from the other 7 uses.
 Translations from the Jewish Study Bible.
 The ideas in this paragraph are owed to Jacob Milgrom in his article, “Law, Narrative, and the Exegesis of Leviticus 19”.
 B. Sanh. 60a; Ibn Ezra, Ramban, Bekhor Shor.
 Mikra KiPeshuto, A.B. Ehrlich.
 Talmud Bavli, Yevamot 4b, Yoma 71b.
 See Shemot 28:31 and 39:22, in contrast to Bamidbar 15:39.
 Shemot 19:6.