ביום דבר ה' אל משה בהר סיני, “as long as G-d wasspeaking with Moses at Mount Sinai,” Aaron’s sons Nadav and Avihu were still alive. They died in the Tabernacle in the desert of Sinai, at the beginning of the second year.

ובנים לא היו להם, “and they did not have sons.” Rabbi Yaakov, son of bar Avi, speaking in the name of Rabbi Acha, said: if these sons of Aaron had had sons, they would have preceded Elazar and Ittamar in greatness; it is a rule that anyone who has offspring takes precedence compared to those who do not have heirs. Their shortcoming was that they did not marry and assure themselves of offspring. (Midrash Rabbah Bamidbar 2,22.)

על פני אהרן אביהם, “while their father was alive.” The expression: על פני, is to be understood as in Deuteronomy 21,16: על פני בן השנואה הבכור, “instead of the firstborn son of the hated wife;” or as in Exodus 20,3: לא יהיה לך אלוהים אחרים על פני, “you shall not have any other deities in My presence,”

הקרב את מטה לוי, “bring the tribe of Levi near;” in chapter 1,50, G-d had already told Moses to appoint that tribe to be in charge of all the furnishings of The Tabernacle as well as the Tabernacle itself and to carry it during the journeys; they had also been warned not to allow any non Levite to come close to the Tabernacle; now that the Levites were to be appointed as performing service for the priests (Aaron and descendants), Moses was commanded to

והעמדת אותם, “to present them” to the priests by performing services for them. Use of the root עמד in the in a similar mode is also found Kings I 17,1, where the prophet Elijah saying: ועמדתי לפניו. “I will present myself before him [G-d] as being at his service.”

ושמרו את משמרתו, “and they shall keep his charge (The High Priest’s) in accordance with his instructions.

ואת משמרת כל העדה, “and the charge of the whole congregation;” a reference to anything the Israelites were supposed to do in front of the Tent of Meeting they should see to it that it be done.

לעבוד את עבודת המשכן, “to perform the service of the Tabernacle.” Details had been spelled out already in 1,50.

נתונים נתונים המה לו מאת בני ישראל, “they are wholly given to him (Aaron) from the Children of Israel (to be at his disposal).” We must understand these instructions as applying to the future when the average Israelite will be preoccupied with earning his livelihood as a farmer, and agriculture making demands upon him that cannot be delayed. The Levites, not having ancestral land, had time therefore to devote themselves to those tasks.

ושמרו את כהונתם, “so that the priests could preserve their time for their priestly duties. Their principal concern was to avoid becoming ritually defiled.

והזר, “and the common Israelite, etc.” any Israelite or Levi who presumes to perform the duties of the priests will die.

תחת כל בכור, “in place of every firstborn;” these firstborns also had not been intended to inherit ancestral fields, ever, as they were meant to be the priests in their respective families. When the Levites were appointed to perform the tasks previously meant to be performed by the firstborn, they forfeited their claim to ancestral heritage in the Land of Israel, and the firstborns, after redemption, could then lay claim to ancestral territory as did all the non firstborn.

.מבן חדש ומעלה תפקדם, “you will count them from one month and up.” The reason why they were not counted from twenty years and up is that they would not participate in any wars, and from 30 days of age and up they could be used to redeem firstborns of the other tribes. A first born son of any tribe became viable at the age of 30 days.

המשכן, this refers to the carpeting of twisted linen which formed part of the roof of the Tabernacle.

והאהל, “and the tent;” these are the carpets made of goats’ hair.

מכסהו, “its covering;” this is a reference to the hides of red dyed rams and the hides of the animal known as tachash.

אשר על המשכן ועל המזבח, “which are next to the Tabernacle and the copper altar.”

In this verse the word משכן refers to the courtyard surrounding that structure.

ולקהת משפחת העמרמי, “and of Kehat, the family of Amram;” we are now speaking of the antecedents of Moses, not including any of Aaron’s family; this is why we read in Chronicles I 23,13: ויבדל אהרן להקדישו קדש קדשים, “Aaron was separated to sanctify him to become most holy.”Moses and his sons were considered as simply members of the tribe of Levi.

וכלי הקודש, “and the holy vessels;” these are the ones enumerated further on.

אשר פקד משה ואהרן, “whom Moses and Aaron had counted.” There are dots on the word ואהרן.

קח את הלוים תחת כל בכור בבני ישראל, “take the Levites in exchange for all the firstborn of the remainder of the tribes of Israel.” The reason why the Levites alive now were not used to also redeem the Israelites that were to be born during the 38+years that the Israelites were still to wander through the desert, is because the Levites that were sanctified now had already been born by other Levites who had redeemed firstborns. It is not logical to assume that they possessed the spiritual power to redeem a second time. All the firstborns that are mentioned at this point were not the ones that had been redeemed by Levites in the desert, but had been born by ordinary Israelites who had never been redeemed; the firstborns that had been redeemed by Levites had not been known to also redeem as yet unborn firstborn that stemmed from them.

חמשת חמשת שקלים לגלגלת, “five shekel apiece per head count;” this was the standard amount for redeeming firstborns.

ונתת הכסף לאהרן ולבניו, “you are to give the money to Aaron and his sons; just as the Levites who had redeemed the firstborn now took the place of them, so the money realized from the 273 firstborn for whom no Levites were found to redeem them, now was given to the priests, seeing that the Levites themselves were also subservient to the priests.

מאת בכור בני ישראל, “from the firstborn of the Children of Israel;” this refers to the 273 who were in excess of the 22000 firstborns listed earlier.