אש זרה ומה שלפני מות בני אהרון

Moses and Aaron then went inside the Tent of Meeting. When they came out, they blessed the people; and the Presence of יהוה appeared to all the people. Fire came forth from before יהוה and consumed the burnt offering and the fat parts on the altar. And all the people saw, and shouted, and fell on their faces. Now Aaron’s sons Nadab and Abihu each took his fire pan, put fire in it, and laid incense on it; and they offered before יהוה alien fire, which had not been enjoined upon them. And fire came forth from יהוה and consumed them; thus they died at the instance of יהוה. Then Moses said to Aaron, “This is what יהוה meant by saying: Through those near to Me I show Myself holy, And gain glory before all the people.” And Aaron was silent. Moses called Mishael and Elzaphan, sons of Uzziel the uncle of Aaron, and said to them, “Come forward and carry your kinsmen away from the front of the sanctuary to a place outside the camp.”

ויצאו ויברכו את העם AND THEY CAME OUT AND BLESSED THE PEOPLE — They said the words that conclude “The Prayer of Moses” (Psalms 90:17): “May the beauty of the Lord our God be upon us” — i. e. May it be God’s will that the Shechinah may rest upon the work of your hands (see Rashi on Exodus 39:43). They invoked just this blessing and not another formula because during the whole seven days of the installation when Moses was setting up the Tabernacle and officiating therein and dismantling it daily the Shechinah had not rested upon it and the Israelites felt ashamed, saying to Moses: “O, our Teacher Moses! All the trouble which we have taken was only that the Shechinah may dwell amongst us, so that we may know that the sin of the golden calf has been atoned for on our behalf!” He therefore had said to them (v. 6): “This is the thing which the Lord commanded that ye should do so that the glory of the Lord may appear unto you” (i. e. only after these offerings will have been brought by Aaron (cf. v. 7) will God’s glory appear unto you). My brother Aaron is more worthy and excellent than I am, so that through his sacrifices and ministration the Shechinah will rest upon you, and ye will thereby know that the Omnipresent God has chosen him to bring His Shechinah upon you.

20) (Vayikra 9:24): "And a fire came forth from before the L–rd": When they saw a new fire descending from on high and lapping up upon the altar the burnt-offering and the fats, they opened up their mouths in song. And of that moment it is written (Tehillim 33:1): "Sing joyfully, you righteous ones, in the L–rd. Praise (of the L–rd) becomes the just."

22) A different view: When the sons of Aaron saw that all the offerings had been sacrificed and all the services performed and that the shechinah had not descended for Israel, Nadav said to Avihu: Now is there such a thing as cooking a meal without fire? — whereupon they took a strong fire and entered the holy of holies, viz. (Tehillim 33:24): "And the sons of Aaron took, each his coal pan, and they put the fire therein" — at which the Holy One Blessed be He said to them: I will honor you more than you have honored Me. You have brought before Me an impure fire; I will burn you with a pure fire.

ועל פני כל העם אכבד AND BEFORE ALL THE PEOPLE I WILL BE HONOURED — When the Holy One, blessed be He, executes judgment upon the righteous He becomes feared, and exalted and praised. If this be so in the case of these (when He judges the righteous) how much more is it so in the case of the wicked (i. e. when He punishes the wicked)! And in a similar sense it says (Psalms 68:36) “Thou art feared, O god, ממקדשיך”. Read not here מִמִּקְדָשֶׁיךָ, “from out of Thy sanctuaries”, but ‎ ‏ מִמִּקֻדָּשֶׁיךָ“because of Thy sanctified ones” (Zevachim 115b).