John Gill Commentary Numbers 3

These also [are] the generations of Aaron and Moses
The descendants of them, those of the former, who is named first, because the eldest, were priests, and those of the latter Levites, and who are not very plainly pointed at, but are included among the Amramites, (Numbers 3:27) ; the posterity of Moses being very obscure, only Levites, and these not particularly named but swallowed up among the Kohathites: find the following account was as it stood,

in the day [that] the Lord spoke with Moses in mount Sinai ;
and not, altogether as it then, was when he spoke to him in the wilderness, of Sinai, for then Aaron had four sons, but now two of them were dead as is after observed; and it seems to be for the sake of this circumstance chiefly that this clause is so put.

And these [are] the names of the sons of Aaron
The Targum of Jonathan adds, disciples of Moses, the master of the Israelites; none of the posterity of Moses being expressly, named; Jarchi observes, that the sons of Aaron are called the generations of Moses, because he taught them the law; for whoever, he says, teaches his neighbour's son, the law, the Scripture accounts of him as if he begat him, see (1 Corinthians 4:15) ;

Nadab the firstborn, and Abihu, Eleazar and Ithamar ;
as in (Exodus 6:23) .

These [are] the names of the sons of Aaron, the priests that
were anointed
With the holy, anointing oil, with which they were anointed when, Aaron was and they only, see (Exodus 30:30) ;

whom he consecrated to minister in the priest's office ;
that is, whom Moses consecrated, by anointing them, putting the priest's garments on them, offering sacrifice for them, and filling their hands with sacrifices which is the phrase here used for consecration: see (Exodus 29:15–24) .

And Nadab and Abihu died before the Lord, By flaming fire, as the Targum of Jonathan adds, see (Leviticus 10:2); and so were not alive at this time when the account of the priests and Levites was taken:

when they offered strange fire before the Lord in the wilderness of Sinai; after the tabernacle was set up, and the service of it begun, and quickly after their unction and consecration: of this strange fire, (See Gill on Numbers 10:1);

and they had no children; which is observed, partly to show the punishment of them, and the reproach upon their names, that they died childless, and had none to succeed them in the priesthood; for as the Jewish writers ^F14 observe if they had left any behind them, those would have come into the office before Eleazar and Ithamar; and partly to show that all the priests in succeeding ages sprung from those next mentioned:

and Eleazar and Ithamar ministered in the priest's office, in the sight of Aaron their father; in his presence, under his inspection, and by his direction, he seeing and observing that they did everything according to the laws delivered by Moses, relating to, the office of the priesthood; or while he was yet alive, as Aben Ezra, they were concerned with him, and acted under him in the priestly office; and so the Septuagint version renders it, "with Aaron their father" ^F15; but a Jewish writer ^F16 interprets it in a different manner, "in the room of Aaron their father"; as if it respected not any conjunction with him in the then present exercise of their office in his lifetime, but their succession in it after his death; but the former seems most correct.

FOOTNOTES:

• F14: Torat Cohanim apud Ceseph Misnah in Maimon. Melachim, c. 1. sect. 7.
  Chaskuniin in loc.
• F15: Which is approved by Noldius, p. 731.
• F16: Chaskuni.

And the Lord spoke to Moses
After he had given him the order for the numbering the children of Israel, and for the manner of their encampment and journeying:

saying ;
as follows.