Leviticus 10:6

The ordinary priest might defile himself for those near of kin (Leviticus 21:2) but the high priest was not allowed to do so (Leviticus 21:11). On this occasion Aaron, Eleazar, and Ithamar were all subject to the stricter rule. The whole house of Israel joined in the mourning.

Let not the hair of your heads go loose It was said to Ezekiel when forbidden to mourn, -bind thy headtire upon thee" (Ezekiel 24:17). On removing the headtire the hair would fall down, so that the prohibition -Uncover not your heads" (A.V.), is in effect the same. To let the hair loose and to rend the garments were and still are signs of mourning among the Jews and Eastern nations.