||Moses said to Aaron and his sons, Eleazar and Ithamar, 'Do not go without a haircut and do not tear your vestments; otherwise you will die, bringing divine wrath upon the entire community. As far as your brothers are concerned, let the entire family of Israel mourn for the ones whom God burned.
Vayomer Moshe el-Aharon ule-El'azar ule-Itamar banav rasheychem al-tifra'u uvigdeychem lo-tifromu velo tamutu ve'al kol-ha'edah yiktsof va'acheychem kol-beyt Yisra'el yivku et-hasrefah asher saraf Adonay.
|Eleazar and Ithamar|
Aaron's younger sons (Exodus 6:23).
|go without a haircut|
(Sifra; Rashi; Saadia). This is because they were now like high priests; see Leviticus 21:10 (Rashbam; Ramban). This indicates that they were not allowed to let their hair grow for 30 days without being cut (Sanhedrin 22b; Yad, Biyath HaMikdash 1:11).
This also teaches that it was forbidden for them to perform any divine service if they went without a haircut for more than 30 days (Ramban on Sefer HaMitzvoth, Negative 73, 163). Some say that it was even forbidden for them to enter the sanctuary without a haircut (Yad, Biyath HaMikdash 1:8; Sefer HaMitzvoth, Negative 163). Others maintain that as long as the Temple stood, a priest could not go without a haircut for more than 30 days under any conditions (Raavad, Biyath HaMikdash 1:9. from Ezekiel 44:20; cf. Kesef Mishneh ibid.; Sanhedrin 22b).
From here we learn that a mourner normally may not cut his hair for 30 days (Moed Katan 14b).
|do not tear|
(Rashi; Ibn Ezra). Param in Hebrew. Or, 'do not unravel stitches' (Rashi, Makkoth 22b, s.v. VeNiframu; Radak, Sherashim; Arukh). According to others, param denotes pulling cloth apart so that its weave unravels, rather than tearing it cleanly (Rambam on Sotah 1:5), or in general, tearing it very badly (Rashi, Sotah 7a, s.v. VeIm).
This is because a priest is forbidden to enter the temple with torn vestments (Yad, Biyath HaMikdash 1:14; Sefer HaMitzvoth, Negative 164).
It is from here that we see that a mourner must rend his garments (Moed Katan 15a).