The argument is, that as such meals were appointed in honor of Yahweh Himself, they ought to be conducted with due reverence and discretion.

Leviticus 10:12

Beside the altar - What is called "the holy place" in Leviticus 10:13, Leviticus 10:17 : it should be rather, a holy place, any part of the holy precinct, as distinguished from a merely "clean place" Leviticus 10:14, either within or without the court of the tabernacle.

And Moses spake unto Aaron, and unto Eleazar, and unto Ithamar, his sons that were left,.... Of the burning, as the Targum of Jonathan; who survived his other two sons that were burnt, who remained alive, not being concerned with them in their sin, and so shared not in their punishment:

take the meat offering that remaineth of the offerings of the Lord made by fire; for all but the handful that was burnt of that kind of offerings belonged to the priests, see Leviticus 6:14 this meat offering, according to Jarchi, was the meat offering of the eighth day, that is, of the consecration, or the day after it was finished, on which the above awful case happened, Leviticus 9:17 and also the meat offering of Nahshon the son of Amminadab, of the tribe of Judah, who offered his offering first at the dedication of the altar, on the day the tabernacle was set up, which he supposes was on this day, see Numbers 7:1, now these meat offerings were not as yet eaten, and which may be true of the first of them, wherefore Aaron and his sons, notwithstanding their mourning, are bid to take it:

and eat it without leaven beside the altar: the altar of burnt offering in the court of the tabernacle, as directed See Gill on Leviticus 6:16,

for it is most holy: and so might be eaten by none but holy persons, such as were devoted to sacred services, and only in the holy place, as follows; within hangings, where the most holy things were eaten, as Jarchi, that is, within the court of the tabernacle, which was made of hangings.

After the directions occasioned by this judgment of God, Moses reminded Aaron and his sons of the general laws concerning the consumption of the priests' portions of the sacrifices, and their relation to the existing circumstances: first of all (Leviticus 10:12, Leviticus 10:13), of the law relating to the eating of the meat-offering, which belonged to the priests after the azcarah had been lifted off (Leviticus 2:3; Leviticus 6:9-11), and then (Leviticus 10:14, Leviticus 10:15) of that relating to the wave-breast and heave-leg (Leviticus 7:32-34). By the minchah in Leviticus 10:12 we are to understand the meal and oil, which were offered with the burnt-offering of the nation (Leviticus 9:4 and Leviticus 9:7); and by the אשּׁים in Leviticus 10:12 and Leviticus 10:15, those portions of the burnt-offering, meat-offering, and peace-offering of the nation which were burned upon the altar (Leviticus 9:13, Leviticus 9:17, and Leviticus 9:20). He then looked for "the he-goat of the sin-offering," - i.e., the flesh of the goat which had been brought for a sin-offering (Leviticus 9:15), and which was to have been eaten by the priests in the holy place along with the sin-offerings, whose blood was not taken into the sanctuary (Leviticus 6:19, Leviticus 6:22); - "and, behold, it was burned" (שׂרף, 3 perf. Pual). Moses was angry at this, and reproved Eleazar and Ithamar, who had attended to the burning: "Wherefore have ye not eaten the sin-offering in a holy place?" he said; "for it is most holy, and He (Jehovah) hath given it you to bear the iniquity of the congregation, to make atonement for it before Jehovah," as its blood had not been brought into the holy place (הוּבא construed as a passive with an accusative, as in Genesis 4:18, etc.). "To bear the iniquity" does not signify here, as in Leviticus 5:1, to bear and atone for the sin in its consequences, but, as in Exodus 28:38, to take the sin of another upon one's self, for the purpose of cancelling it, to make expiation for it. As, according to Exodus 28:38, the high priest was to appear before the Lord with the diadem upon his forehead, as the symbol of the holiness of his office, to cancel, as the mediator of the nation and by virtue of his official holiness, the sin which adhered to the holy gifts of the nation (see the note on this passage), so here it is stated with regard to the official eating of the most holy flesh of the sin-offering, which had been enjoined upon the priests, that they were thereby to bear the sin of the congregation, to make atonement for it. This effect or signification could only be ascribed to the eating, by its being regarded as an incorporation of the victim laden with sin, whereby the priests actually took away the sin by virtue of the holiness and sanctifying power belonging to their office, and not merely declared it removed, as Oehler explains the words (Herzog's Cycl. x. p. 649). Exodus 28:38 is decisive in opposition to the declaratory view, which does not embrace the meaning of the words, and is not applicable to the passage at all. "Incorporabant quasi peccatum populique reatum in se recipiebant" (Deyling observv. ss. i. 45, 2).

(Note: C. a Lapide has given this correct interpretation of the passage: "ut scilicet cum hostiis populi pro peccato simul etiam populi peccata in vos quasi recipiatis, ut illa expietis." There is no foundation for the objection offered by Oehler, that the actual removal of guilt and the atonement itself were effected by the offering of the blood. For it by no means follows from Leviticus 17:11, that the blood, as the soul of the sacrificial animal, covered or expiated the soul of the sinner, and that the removal and extinction of the sin had already taken place with the covering of the soul before the holy God, which involved the forgiveness of the sin and the reception of the sinner to mercy.)

And Moses spake unto Aaron, and unto Eleazar and unto Ithamar, his sons that were left, Take the meat offering that remaineth of the offerings of the LORD made by fire, and eat it without leaven beside the altar: for it is most holy:

10:12 Eat it - Moses repeats the command, partly lest their grief should cause them to neglect their meat prescribed by God, (which abstinence would have been both a signification of their sorrow which God had forbidden them, and a new transgression of a divine precept;) and partly to encourage them to go on in their holy services, and not to be dejected, as if God would no more accept them or their sacrifices.

12-15. Moses spake unto Aaron, &c.-This was a timely and considerate rehearsal of the laws that regulated the conduct of the priests. Amid the distractions of their family bereavement, Aaron and his surviving sons might have forgotten or overlooked some of their duties.

10:12-20 Afflictions should rather quicken us to our duty, than take us from it. But our unfitness for duty, when it is natural and not sinful, will have great allowances made for it; God will have mercy, and not sacrifice. Let us profit by the solemn warning this history conveys. When professing worshippers come with zeal without knowledge, carnal affections, earthly, light, vain, trifling thoughts, the devices of will-worship, instead of the offering of soul and spirit; then the incense is kindled by a flame which never came down from heaven, which the Spirit of a holy God never sent within their hearts.