What were the "Bigdei ha'Serad"?
Rashi and Seforno: They were the covers of Techeiles, Argaman and Tola'as Shani 1 with which Aharon and his sons covered the Keilim before they traveled. 2
Ramban (citing Yoma 72a-b) and Da'as Zekenim: The Bigdei S'rad are synonymous with Bigdei Kehunah.
Refer to 31:10:2:2*..
As described at the end of Parshas Bamidbar (Rashi and Rashbam). It cannot be referring to the Bigdei Kehunah a. because the Torah continues "ve'es Bigdei ha'Kodesh le'Aharon ha'Kohen ... "; and b. because the Pasuk 39:1, states that the Bigdei ha'Serad were made of Techeiles, Argaman and Tola'as Shani, and does not mention Sheish (linen) - whereas all the Bigdei Kehunah which contained Argaman and Tola'as Shani also contained Sheish. The Torah does not provide specifications, because they had no specific shape or size, and they commonly made network coverings, to fit over the Keilim (Seforno).
Why were they called "Bigdei ha'Serad"??
Rashi #1: It means 'garments of service'. 1
Rashi #2 and Rashbam: Because they were knitted (plaited with holes). 2
Ramban #1 (citing Ibn Ezra): Because each cover was made of one specific species. 3
Although it does not appear in any other context (Rashi).
See Targum Onkelos in Terumah, 27:9 on the word "Kela'im" and on the word "Michbar" (Ibid. 27:4). Refer also to 27:9:1:1* The Ramban objects to this explanation, since it is not appropriate to cover the holy Keilim with knitted cloths with holes.
As in Yo'el, 3:5 and in Yehoshua, 10:20 (Ramban).
See Ramban, DH 'veha'Oleh mi'Divrei Raboseinu'.
Why did the Torah not instruct Moshe to make the Bigdei ha'Serad like it did all the other parts of the Mishkan?
Ramban (explaining Rashi) 1 : Hashem, not particular as to how they covered the Keilim, left it up to them to make whatever covers they saw fit. Based on their decision to make individual covers of Techeiles, Argaman and Tola'as Shani, Hashem instructed them to use the Techeiles cover for the Aron, the Argamon for the Mizbe'ach and the Tola'as Shani for the Shulchan.
Refer to 31:10:1:1*.
