פירוש על ויקרא 20:7

והתקדשתם SANCTIFY YOURSELVES — This implies keeping aloof from all idolatry (Sifra, Kedoshim, Chapter 10 2).

והתקדשתם, by staying clear of all incestuous relationships.

והתקדשתם והייתם קדושים, "and sanctify yourselves so that you will be holy." G'd directs that we should strive to be holy; when people do this they are assured of attaining the spiritual level of angels who are called קדושים, "holy beings." We know this from Daniel 8,13 "ויאמר אחד קדוש," "one holy one said, etc." This is what is meant by והייתם קדושים. Our sages in Bamidbar Rabbah 20, comment on Numbers 23,23 כעת יאמר ליעקב ולישראל מה פעל אל. "at a time when Jacob as well as Israel is told at once what G'd had worked." They describe an outer circle of angels and an inner circle of Israelites. The angels who are standing in the outer circle are forced to ask the Israelites (who are closer to the centre) what G'd has been doing. This teaches that when the Bible speaks of "His holy ones" in a context of angels, the reference is to the Jewish people. In verse 8 the Torah specifies the means by which the Israelites are to sanctify themselves by saying: ושמרתם את חוקותי ועשיתם אותם. The word ושמרתם refers to observance of negative commandments, whereas the word ועשיתם refers to the performance of positive commandments. Between them the commandments are the means by which G'd will sanctify us. The Torah associates G'd's four lettered name י־ה־ו־ה with the performance of the commandments. The Tikkuney Ha-Zohar chapter 70 explain how by the performance of each commandment the respective organ with which that commandment is performed merits that G'd's name comes to rest on it, a concept alluded to in the letters of the word מצוה.

This [refers to] separation from idolatry. Even though [Rashi] said above (Vayikra 19:2), “Wherever you find a fence against sexual crime, you find holiness,” which implies that the term “sanctity” only applies to sexual matters, the answer is that idolatry is also called a harlot (זונה) as it says here “To go astray (לזנות) after Molech.”

והייתם קדושים, so that your seed will merit that the Divine Presence will dwell among the likes of him. Our sages are on record that “the Divine presence will rest only on those Jewish families that are genealogically pure.” (Kidushin 70)

כי אני ה' אלוקיכם, the One Who said to Avraham “to be your G’d and that of your seed after you.” (Genesis 17,7) What was meant by the word לזרעך was the seed which is genealogically yours in an uncontaminated state. (as explained by Bamidbar Rabbah 12,4)