Rabbi Yakov Haber
"As G-d Commanded Moshe"
The recurrent phrase in this week's parasha - "ka'asher tziva Hashem es Moshe" - is repeated no less than eighteen times. The commentaries offer diverse explanations for this phenomenon ranging from technical to halachic to hashkafic. Some distinguish between our parasha where the phrase appears and parashas VaYakheil where the phrase curiously does not appear.
Rav Meir Simcha of Dvinsk in his Meshech Chachma explains that the bigdei kehuna described in Pekudei contained sha'atnez - wool and linen - and therefore required special Divine dispensation to wear them. The Mishkan, whose construction is mentioned in VaYakheil, by contrast, even though its curtains also contained sha'atnez, but no regular Torah prohibition was violated since they were not worn. Hence, the Torah indicates that the Jewish people acted as G-d commanded concerning the bigdei kehuna. Concerning the Mishkan, this was obvious.
Rav Hirsch comments that the Mishkan, a building, was not considered complete until it was totally finished. By contrast, the garments of kohanim were considered complete as each one was finished. Hence, in our parasha, the above-mentioned phrase appears after the formation of each garment indicating its completion and also concerning the completion of the construction of the Mishkan after all of its vessels, walls and curtains were formed (Pekudei 39:42-43).
Beis HaLevi, the first Rav Yosef Dov HaLevi Soloveitchik, presents a penetrating analysis of this recurring phrase in two places. In parashas Lech L'cha, Beis HaLevi explains this phrase to indicate that even though an individual is highly intelligent and thinks that he knows the reason why Hashem commanded the mitzva, he should perform it not because of his knowledge of the reason but because of the Divine command itself. Only this attitude is truly Divine service. Performing the mitzva because of our understanding would not be serving G-d but serving ourselves by following our understanding. A similar duality appears in the Gemara Rosh HaShana (16a). After the Gemara questions why we blow the shofar on Rosh HaShana, the Gemara challenges the question: Why do we blow shofar?! Hashem commanded us to blow! Even though ta'amei hamitzvos are often offered by Torah scholars as part of Torah study, the m'chayeiv, that which obligates us to do the mitzva is certainly not the reason, but rather the Divine command itself (see P'nei Yehoshua). Whether one has an insight into a possible reason or not, he is equally bound by the mitzva because of the Divine commandment.
In parashas Ki Tissa, Beis HaLevi links this concept to the relationship between the Cheit Ha'Eigel and the building of the Mishkan. One opinion in the Midrash followed by Rashi (Ki Tissa 31:18) states that Hashem commanded Moshe concerning the Mishkan only after the Cheit Ha'Eigel. Thus, the construction of the Mishkan atoned for the sin of the Golden Calf. Beis HaLevi explains that each mitzva has enormous spiritual, inner depth and this is certainly so for the Mishkan and Mikdash which "houses" the Divine Presence in some mysterious way. One knowledgeable of this depth of Torah might be tempted to utilize his knowledge to create some entity which will bring down the Divine Presence without following any specific Divine commandment. This is what B'nei Yisrael attempted to do in forming the Eigel. (See Midrash quoted by Ramban (32:1) that they were inspired to make an image of the Eigel having witnessed the image of an ox in the Merkava vision they experienced at Har Sinai (see Yechezkel 1:10).) Their grievous error lay in the fact that only G-d determines what form of worship is appropriate and what kind of structure and vessels would be a correct form to "house" the Shechina. K'lal Yisrael in constructing the Mishkan atoned for their great sin by not diverging one iota from the Divine command and building it because of G-d's command, not based on their insights into its enormous spiritual significance. Creating alternate forms of worship based on the perceived reasons for mitzvos is sinful and can even lead, as it did in the case of the Eigel, to idolatry.
Perhaps we can connect all of the approaches given above as follows. Divine service is itself a big mystery. How can finite man serve the infinite Creator? As the Midrash (B'reishis Rabba 44:1) teaches, G-d is not affected by our service of Him. Nonetheless, Hashem Yisborach in His Infinite Wisdom provides for us a means with which to serve Him and elevate ourselves through that service. The unifying factor of all of these approaches is that only G-d can command how His creations should serve and thereby connect to the Infinite One.
When should one mitzva override another? Only the Torah itself can determine that. This is Meshech Chachma's teaching - the overriding of the law of sha'atnez is only "as G-d commanded Moshe." What if we think we know the reason for a mitzva - shouldn't it be performed because of that reason? This is what Beis HaLevi teaches: our performance of mitzvos is in order to follow the Divine command. The reasons can enhance but should never motivate the "mitzva act". What if we come up with a new mode of service? This is the second teaching of Beis HaLevi: only G-d can determine the mode of service appropriate.
But G-d also commanded the Chachmei HaDor to create safeguards to the Torah and even add Rabbinic mitzvos. Ran (D'rashos 7) teaches that these serve as expressions of ahavas Hashem and yir'as Hashem demonstrating that we do not wish to suffice with just the minimum requirements and also wish to safeguard our precious heritage. However, since we cannot choose to serve the Almighty in a way he has not commanded, the Chachmei HaDor must have enormous insight as to what kinds of Rabbinic safeguards and Rabbinic mitzvos would "blend in" with the rest of the Torah and which would be foreign intrusions into the Torah system. Our sages teach us "kol d'tikkun Rabbanan k'ein d'Oraisa tikkun". All Rabbinic enactments follow Torah patterns. To do so properly requires absolute mastery of the Torah far beyond that which ordinary Torah scholars possess.
Recent controversies have erupted concerning what modes of avodas Hashem are appropriate and which are not. Our parasha resonates again and again with the slogan - "ka'asher tziva Hashem es Moshe." Make sure that everything is in accordance with this directive! But how are we to know Hashem's Will in an era when we can no longer ask Moshe Rabbeinu to receive direct instructions from the Almighty? The answer is contained in the Torah's directive "ki yipalei mim'cha davar lamishpat...v'asisa k'chol asher yorucha" (Shof'tim 17:8-10). Follow the interpretations and rulings of the Sanhedrin and in subsequent eras the G'dolei Chachmei haDor (see Seifer haChinuch (495) that this verse applies for all generations) who will be given Divine assistance to determine which mode blends in with the Torah and which does not. May the Nosein HaTorah continue to grant the Chachmei haDor the wisdom to guide us in following His will and Am Yisrael the desire to loyally follow their guidance.
 Be'er Moshe by R. Moshe Yechiel HaLevi of Ozhorov suggests the Moshe Rabbeinu who was willing to give up his life for K'lal Yisrael merited "chai" mentionings of this phrase referencing his role as the sh'liach of Hashem indicating his eternal life and legacy.
See Rav Y. D. Soloveitchik's shiur on the Korach Rebellion available at www.bcbm.org.
 The important distinction between the Sages until the chasimas haTalmud and those after that time is beyond the scope of our limited words here. But even current Chachmei HaDor are charged to make limited takkanos to preserve the Torah's integrity.