We would like to understand the nature of Kedusha.
Chazal [Niddah 30a] said that a fetus takes an oath:
"הוי יודע שהקב"ה טהור ומשרתיו טהורים ונשמה שבך טהורה היא אם אתה משמרה בטהרה מוטב".
"Know that Hashem is pure, his servants are pure and the neshama within you is pure, if you guard it with purity - good."
A mention is made of purity - טהרה - but not of holiness - קדושה, as the pasuk says "קדושים תהיו כי קדוש אני ה' א-להיכם". The fundamental distinction between קדושה and טהרה is that טהרה implies that there is also טומאה while קדושה is the complete release from טומאה, not only distancing oneself from טומאה but completely removing it from the world. As long as the נשמה is outside the body it can perceive Hashem on the level of טהרה with the potential for טומאה still present. After the נשמה enters the body and elevates it to the level of נשמה then it is possible to perceive the level of קדושה of קדושים תהיו כי קדוש אני. And in the future when the pasuk "ואת רוח הטומאה אעביר מן הארץ" - "The spirit of impurity I will remove from the land" is fulfilled and "ונשגב ה' לבדו ביום ההוא" - "Hashem will stand alone on that day" - then קדושה will be revealed in its complete glory.
There is a difference between מצוות that were given at מרה and מצוות that were given at סיני. At מרה it says "שם שם לו חק ומשפט ושם נסהו", while at סיני it says "ונתת אל הארון את העדות אשר אתן אליך". The difference is that חק and משפט [laws and statutes] are for the sake of existence while עדות [testimonies] precedes existence, because עדות must be unbiased and a biased witness is פסול לעדות. Since all of our lives flow from the reality of existence we are all biased and so how can be be witnesses to Hashem "אתם עדי ואני א-ל". Just at מתן תורה the Jews merited that their lives would not be based on the order of normative existence but rather they can live from the power of Torah. Therefore, when Moshe ascended to the heavens he did not eat bread nor drink water and he was there for 40 days and forty nights [and according to Chazal - 3 times 40 days and nights] - a different otherworldly existence. And Moshe was a member of Klal Yisrael and the rule is that:
"דבר שהיה בכלל ויצא מן הכלל לא ללמד על עצמו יצא אלא ללמד על הכלל כולו יצא"
Something that was included in the כלל and then went out of the כלל does not teach about itself but about the entire כלל. So essentially Moshe was teaching us that ALL of כלל ישראל could live such a otherworldly, angelic existence. Because of the level they were on, they were no longer considered biased and were kosher witnesses to testify about Hashem.
The Medrash says:
ואתה מרום רוממות אתה נוהג בעולמך - נתת כהונה לאהרן לעולם "ברית מלח היא" נתת מלכות לדוד לעולם שנאמר (ד"ה ב יג) "הלא לכם לדעת כי אלהי ישראל נתן ממלכה לדוד על ישראל לעולם". נתת קדושה לישראל לעולם שנאמר "קדושים תהיו":
This means that even though כהונה and מלכות are very sublime and exalted. כהונה extends from Aharon and his sons to the entire Jewish people making it possible for us all to be a "ממלכת כהנים וגוי קדוש". And מלכות בית דוד inspires all of כלל ישראל to accept upon themselves the yoke of heaven. Nevertheless, it was enough for כהונה to be given to Aharon and sons and מלכות to דוד, but קדושה could only be given to כלל ישראל as a whole. Not only כלל ישראל in every generation but כלל ישראל from the beginning of time until the end. That is what the medrash meant when it said that according to Rebbe Akiva ואהבת לרעך כמוך - זה כלל גדול בתורה and בן עזאי said that the pasuk "זה ספר תולדות האדם" is an even bigger rule. In other words - it is not enough to include oneself in the generation in which he lives but he must rather include himself in all of the previous and future generations as well. All together they constitute a complete "book" and that is a כלל even greater than the כלל of ואהבת לרעך כמוך.
כלל ישראל in all of the generations can receive the קדושה of the future "ונשגב ה' לבדו ביום ההוא" and "והיה ה' למלך על כל הארץ ביום ההוא יהיה ה' אחד ושמו אחד" - in other words, Hashem and His holy nation who are שמו "his name" will be One and then then the spirit of impurity will be removed from the land and Hashem will be One with complete unity like no other.
