Comentario citado sobre Levítico 10:6

ותצא אש מלפני ה' ותאכל אותם וימותו לפני ה, “Fire came forth from the presence of the Lord and consumed them, and they died in the presence of the Lord.” Seeing that they had sinned by abusing fire, they were punished by fire. The kind of death described here by the words “in the presence of the Lord” means that their body and soul underwent a “surgical” separation, the fire entering their bodies through their nostrils separating soul from body. We must be careful not to understand the verse as saying that their souls were burned, i.e. that they lost their claim to the hereafter. If that were so the words בקרובי אקדש, “by those very close to Me I become sanctified,” which Moses told Aaron in G’d’s name, would not make any sense. Why should the souls of people G’d describes as close to Him be destroyed, burned?
In reference to verse 3 our sages (Tanchuma Shemini 1) quote Moses as saying to his brother Aaron: “I knew all along that the Sanctuary would be sanctified (that someone prominent would die), but I thought it would be either I or you. Now I know that Nadav and Avihu are greater than either you or I, as G’d has chosen them to sanctify His name.” No doubt such statements are not made concerning people who have lost their claim to the hereafter. There cannot be any doubt that their very death was the atonement for their sin, that they were elevated to the celestial regions immediately and that this is the reason the story of their death is repeated in connection with the atonement rites described in Acharey Mot (Leviticus chapter 16).
In the Jerusalem Talmud Yuma 1,1 the question is raised why the death of Nadav and Avihu is mentioned in connection with Yom Kippur, seeing their deaths occurred on the first of Nissan? The answer given is that the (premature) death of the righteous acts as atonement for the people left alive.
Just as it is wrong to understand the “burning” of these sons of Aaron literally as far as their souls are concerned, so it is wrong to understand the word as referring to the burning of their bodies or even their clothing. After all, the Torah writes (verse 5) that “they carried them (out of the Sanctuary) in their tunics.” Each of these sons of Aaron had his individual tunic as we know from Exodus 28,40. The text refers to their death as “burning,” as we know from verse 6 where the Children of Israel as a whole are commanded to weep “for the conflagration which had befallen, which the Lord had ignited.”

וחומרת – shrinks/curls – the language of (Lamentations 2:11): “My heart is in tumult”; and we derive it from the sons of Aaron as it says concerning them (Leviticus 10:6): “all the house of Israel shall bewail the burning [that the LORD has wrought],” but their bodies were not burned, for it is written (Leviticus 10:5): “They came forward and carried the out of the camp by their tunics…” Here too the command if burning is fulfilled even though only their bowels were burned alone, and this is more preferable as is it written (Leviticus 19:18): “Love your fellow as yourself…”, choose for him a good death.

פרע — The word פרע is punctuated (as to its first syllable) with Patach-Katan (Segol) because it is in construct state to שער ראשו and the meaning is: the פרע, the wild growth of שער ראשו — The meaning of the word פרע is over-growth of the hair; similar is (Leviticus 21:10) “He shall not let his hair grow wild (יפרע)”. Growth of the hair of less than thirty days’ duration does not come under the term פרע (Sifrei Bamidbar 25; Sanhedrin 22b).