Leviticus 10:6

“And Moses said unto Aaron, and unto Eleazar, and unto Ithamar, his sons, etc.] His two younger sons, which yet remained; and so the Septuagint version adds, as in (<031012>Leviticus 10:12,16) uncover not your heads; that is, do not take off your mitre, as the Septuagint version; or the bonnets which they wore in the time of their ministry; for the Jewish priests always had their mitres and bonnets on when they sacrificed; in imitation of which, the Heathens had their heads covered when they offered their sacrifices f201: now it was the way, or custom of a mourner, as Ben Melech observes, to remove his mitre, bonnet, or tiara, from his head; but in this case, that no sign of mourning might be…”

“Uncover not your heads--They who were ordered to carry out the two bodies, being engaged in their sacred duties, were forbidden to remove their turbans, in conformity with the usual customs of mourning; and the prohibition "neither rend your garments," was, in all probability, confined also to their official costume. For at other times the priests wore the ordinary dress of their countrymen and, in common with their families, might indulge their private feelings by the usual signs or expressions of grief.”

“Aaron and his two surviving sons are forbidden to show the accustomed signs of mourning, or to leave the court of the tabernacle in order to attend the funeral, because, from their office, they were especially concerned as consecrated priests in outwardly maintaining the honor of Yahweh. They were to bear visible testimony to the righteousness of the punishment of Nadab and Abihu. The people, on the other hand, as not formally standing so near to Yahweh, were permitted to “bewail” as an acknowledgment that the nation had a share in the sin of its priests. (Compare 1 Corinthians 12:26.) Leviticus 10:6 Uncover not your heads - Or, “set free ... let go loose.” It was a custom to let the hair…”

“Uncover not your head - That is, give no signification of your sorrow; mourn not for them; partly lest you should seem to justify your brethren, and tacitly reflect upon God as too severe; and partly lest thereby you should be diverted from, or disturbed in your present service, which God expects to be done chearfully. But bewail the burning - Not so much in compassion to them, as in sorrow for the tokens of divine displeasure. Leviticus 10:7”

“10:6 Eleazar and Ithamar were Aaron’s two remaining sons (Exod 6:23). • leaving your hair uncombed: This practice and others like it were ways to show grief in biblical times (cp. Gen 37:29; 44:13; Deut 14:1; 2 Sam 1:11; Job 1:20; Jer 16:6; 47:5). As high priest, Aaron was prohibited from participating in these rituals or in any way displaying his grief (Lev 21:10). The injunction extended to Eleazar and Ithamar; if God’s representatives had shown grief on this occasion, it might have been interpreted by observers as disagreeing with God’s justice. However, the laypeople were allowed to mourn.”

“Uncover: Lev 13:45, Lev 21:1-15; Exo 33:5; Num 5:18, Num 6:6, Num 6:7, Num 14:6; Deu 33:9; Jer 7:29; Eze 24:16, Eze 24:17; Mic 1:16 lest wrath: Num 16:22, Num 16:41-47; Jos 7:1, Jos 7:11, Jos 22:18, Jos 22:20; Sa2 24:1, Sa2 24:15-17 Leviticus 10:7”

“Moses prohibited Aaron and his remaining sons from showing any sign of mourning on account of this fatal calamity. "Uncover not your heads," i.e., do not go about with your hair dishevelled, or flowing free and in disorder ( Lev 13:45). ראשׁ פּרע does not signify merely uncovering the head by taking off the head-band (lxx, Vulg., Kimchi, etc.), or by shaving off the hair (Ges. and others; see on the other hand Knobel on Lev 21:10), but is to be taken in a similar sense ראשׁו שׂער פּרע, the free growth of the hair, not cut short with scissors ( Num 6:5; Eze 44:20). It is derived from פּרע, to let loose from anything ( Pro 1:25; Pro 4:5, etc.), to let a people loose, equivalent to giving them…”