This week's parsha, Shemini, starts off with a very ambiguous phrase (Vayikra 9:1):
|א וַיְהִי, בַּיּוֹם הַשְּׁמִינִי, קָרָא מֹשֶׁה, לְאַהֲרֹן וּלְבָנָיו--וּלְזִקְנֵי, יִשְׂרָאֵל.||1 And it came to pass on the eighth day, that Moses called Aaron and his sons, and the elders of Israel;|
All of the commentators scramble to try and figure out what eighth day the Torah is talking about. Rashi says (ibid):
ויהי ביום השמיני: שמיני למלואים, הוא ראש חודש ניסן, שהוקם המשכן בו ביום ונטל עשר עטרות השנויות בסדר עולם (פרק ז)
It was on the Eighth Day: The eighth day of the inauguration (of Aharon and his sons into the priesthood), this was the beginning of the month of Nissan, for the Mishkan (tabernacle) was built on that day and (that day) took ten crowns that are listed in Seder Olam.
Ibn Ezra says (ibid):
ויהי ביום השמיני -היה נראה לנו כי ביום השמיני שמיני לניסן, כי המשכן הוקם באחד לחדש,
And it was on the eighth day: It appears to us that the eighth day is the eighth day of Nissan, because the Mishkan (tabernacle) was built on the first of the month.
In the The Sifra (ibid) it says:
ויהי ביום. השמיני קרא . זה אחד מן הכתובים שצריך
לדרוש . נאמר כאן ויהי ביום ה שמיני ונאמר להלן ויהי
ביומ הש ל י ש י . אין אנו יודעים אם שלישי לשבת אם שלישי למנין
כשהוא אומר כי ביום השלישי ירד ה׳ לעיני כל העם על הר סיני ויה•
ביום השלישי בהיות הב קר הוה אומר שלישי למ נ י ן . וכאן נאמרו
ויהי.ביום השמיני אין אנו יודעים אם שמיני למנין אם שמיני לחדש
כשהוא אומר כי שבעת ימים ימלא את ידכם הוה אומר שמיני
למנין ולא שמיני לחדש :
And it was on the eighth day: This is one of the verses that needs to be expounded upon. It says here "And it was on the eighth day" and it says later on "And it was on the third day." We don't know if this refers to the third day of the week, or the third from counting [from an event]. For when [the Torah] says "On the third day G-D went down, [seen by] the eyes of the entire nation, on Mount Sinai or "And it was on the third day in the morning" it is referring to the third day counting [from some event]. And here it says "And it was on the eighth day" and we don't know if it is the eighth day counting [from the building of the Mishkan] or if it is the eighth day of the month. For when it says "For seven days you will fill your hands" it is talking about Eight days counting [from some event] and not the eighth of the month.
Also, it must be pointed out, as stated by the Torah viMitzva commenting on this Midrash, Chazal were of the opinion that the Mishkan (tabernacle) was erected on the 23 of Adar. For, if they held the Mishkan was erected on the first of Nissan, there is no difference between the eigth of the month of Nissan and the eighth day from the building of the Mishkan, they are the same day.
My point here is to show that this verse is very ambiguous and the true meaning seems to be hidden. However, I think that the meaning of this verse is very deep and in order to fully understand it we must first look at a Maharal and the Gemara in Tractate Megila (10b), first the Gemara:
And it came to pass on the eighth day, and it has been taught, ‘On that day there was joy before the Holy One, blessed be He, as on the day when heaven and earth were created. For it is written, And it came to pass [wa-yehi] on the eighth day, and it is written in the other place, And there was [wa-yehi] one day’?
What is the reason this day is connected to the creation of the world? It is simply because G-D did not complete the creation of the world until this point. What do I mean by that? Adam sinned and was banished from the Garden of Eden at twilight of the sixth day. The seventh day came and G-D's connection to Adam was diminished, which led to G-D's connection to the world becoming diminished. It was not until the erection of the Mishkan and the appointment of Aharon and his son's that G-D now had this close connection to the world.
The Maharal tells us about the unique connection that the tribe of Levi, specifically the Kohanim, have with G-D and how it is only through this connection that G-D really connects to the world. In Ner Mitzva, while talking about the 4 kingdoms that rule in this world before the Moshiach (Messiah) comes, the Maharal explains this idea in depth, I will summarize.
Basically, the world is made up of many different entities and is, therefore, unable to communicate with G-D because G-D is singular. (I am not going to go into this concept right now) However, there is one nation that is able to communicate with G-D and that is because they encompass and embody the idea of singularity. However, even this nation (The Jewish people) are unable to communicate and connect with G-D. It is only through the tribe of Levi that the Jewish people are able to connect to G-D, that is why they work in the Temple. The multiplicity of the world is able to be unified through the Jewish people, who are able to be unified even further into the tribe of Levi, who are able to be unified even further by the Kohanim. Through the Kohanim, the world is able to, once again, communicate with G-D in the Temple. (The whole idea of singularity is a long discussion, just think of it as purity. The world is, essentially, purified through the Kohanim.)
Once we realize this idea, the meaning of "The Eighth day" is clear. It is the "Eighth Day" of creation. The day had arrived, finally, where G-D enabled man to reach the level of communication with Him that was intended for Adam before the sin. That is why this Parsha starts off with Aharon being inaugurated into the Priesthood. This is why the Gemara in Megilah connects this verse to the creation of the world, because this was the final chapter in creation, the creation of a people that can connect to G-D and, through this people (the Jewish people), connect the rest of the world to G-D. For, this is what the Maharal tells us, the Jewish people are the prism that connects G-D to the rest of the world. (Granted, the Kohanim are the prism that connect the Jewish people to G-D, but the Kohanim are part of the Jewish people.)