Why did Hashem see fit to insert this Pasuk?
Rashi: Hashem repeated the instructions (briefly), to render every detail crucial to Aharon and his sons' inauguration. 1
The Gemara in Yoma, 5a, actually learns this from the word "Kachah", which always implies that the issue under discussion is crucial. See Torah Temimah, note 20.
In which respect is the Torah comparing Aharon and his sons?
Yerushalmi, Yoma, 7:3: It teaches us that the Begadim (the Avneit) of the Kohen Hedyot contained Sha'atnez just like those of the Kohen Gadol. 1
What is the significance of the 'Hey' in the word "Osachah"?
Rashi (in Tehilim, 10:8): We have a tradition that on twenty-five occasions in Tanach, the Pasuk writes 'Chaf-Hey' instead of 'Chaf''.
Ha'Kesav ve'ha'Kabalah: The 'Hey' indicates desire. 1
Daf Al ha'Daf (Zevachim 102a, citing the le'Levi Amar): The feminine form hints that Moshe's strength became weak, like a female - because the seven days of the Milu'im correspond to the seven days that Moshe delayed at the burning bush; due to which, the Kehunah did not come from him but from Aharon. 2
Which seven days is the Torah referring to?
Why does the Torah write "Tzivisi Osachah", and not 'Tzivisicha'?
Panim Yafos: To teach Moshe tht, although the commands to build the Mishkan Moshe could fulfill through a Shali'ach. he himself was obligated to offer the Korbanos of the Milu'im and dress Aharon and his sons.
