Carl Friedrich Keil and Franz Delitzsch Old Testament Commentary
The Levites had to allow their obedience to God to be subjected to a severe test. Moses issued this command to them in the name of Jehovah the God of Israel: "Let every one gird on his sword, and go to and fro through the camp from one gate (end) to the other, and put to death brothers, friends, and neighbours," i.e., all whom they met, without regard to relationship, friendship, or acquaintance. And they stood the test. About 3000 men fell by their sword on that day. There are several difficulties connected with this account, which have furnished occasion for doubts as to its historical credibility. The one of least importance is that which arises from the supposed severity and recklessness of Moses' proceedings. The severity of the punishment corresponded to the magnitude of the crime. The worship of an image, being a manifest transgression of one of the fundamental laws of the covenant, was a breach of the covenant, and as such a capital crime, bringing the punishment of death or extermination in its train. Now, although the whole nation had been guilty of this crime, yet in this, as in every other rebellion, the guilt of all would not be the same, but many would simply follow the example of others; so that, instead of punishing all alike, it was necessary that a separation should be made, if not between the innocent and guilty, yet between the penitent and the stiff-necked transgressors. To effect this separation, Moses called out into the camp: "Over to me, whoever is for the Lord!" All the Levites responded to his call, but not the other tribes; and it was necessary that the refractory should be punished. Even these, however, had not all sinned to the same extent, but might be divided into tempters and tempted; and as they were all mixed up together, nothing remained but to adopt that kind of punishment, which has been resorted to in all ages in such circumstances as these. "If at any time," as Calvin says, "mutiny has broken out in an army, and has led to violence, and even to bloodshed, by universal law a commander proceeds to decimate the guilty." He then adds, "How much milder, however, was the punishment here, when out of six hundred thousand only three thousand were put to death!" This decimation Moses committed to the Levites; and just as in every other decimation the selection must be determined by lot or accidental choice, so here Moses left it to be determined by chance, upon whom the sword of the Levites would fall, knowing very well that even the so-called chance would be under the direction of God.
There is apparently a greater difficulty in the fact, that not only did the Levites execute the command of Moses without reserve, but the people let them pass through the camp, and kill every one who came within reach of their sword, without offering the slightest resistance. To remove this difficulty, there is no necessity that we should either assume that the Levites knew who were the originators and ringleaders of the worship of the calf, and only used their swords against them, as Calvin does, or that we should follow Kurtz, and introduce into the text a "formal conflict between the two parties, in which some of Moses' party were also slain," since the history says nothing about "the men who sided with Moses gaining a complete victory," and merely states that in obedience to the word of Jehovah the God of Israel, as declared by Moses, they put 3000 men of the people to death with the sword. The obedience of the Levites was an act of faith, which knows neither the fear of man nor regard to person. The unresisting attitude of the people generally may be explained, partly from their reverence for Moses, whom God had so mightily and marvellously accredited as His servant in the sight of all the nation, and partly from the despondency and fear so natural to a guilty conscience, which took away all capacity for opposing the bold and determined course that was adopted by the divinely appointed rulers and their servants in obedience to the command of God. It must also be borne in mind, that in the present instance the sin of the people was not connected with any rebellion against Moses.
Very different explanations have been given of the words which were spoken by Moses to the Levites (Exo 32:29): "Fill your hand to-day for Jehovah; for every one against his son and against his brother, and to bring a blessing upon you to-day." "To fill the hand for Jehovah" does not mean to offer a sacrifice to the Lord, but to provide something to offer to God (Ch1 29:5; Ch2 29:31). Thus Jonathan's explanation, which Kurtz has revived in a modified form, viz., that Moses commanded the Levites to offer sacrifices as an expiation for the blood that they had shed, or for the rent made in the congregation by their reckless slaughter of their blood-relations, falls to the ground; though we cannot understand how the fulfilment of a divine command, or an act of obedience to the declared will of God, could be regarded as blood-guiltiness, or as a crime that needed expiation. As far as the clause which follows is concerned, so much is clear, viz., that the words can neither be rendered, "for every one is in his son," etc., nor "for every one was against his son," etc. To the former it is impossible to attach any sense; and the latter cannot be correct, because the preterite חיח could not be omitted after an imperative, if the explanatory clause referred to what was past. If כּי were a causal particle in this case, the meaning could only be, "for every one shall be against his son," etc. But it is much better to understand it as indicating the object, "that every one may be against his son and against his brother;" i.e., that in the cause of the Lord every one may not spare eve his nearest relative, but deny either son or brother for the Lord's sake (Deu 33:9). "And to give" (or bring), i.e., so that ye may bring, a blessing upon yourselves to-day." The following, then, is the thought contained in the verse: Provide yourselves to-day with a gift for the Lord, consecrate yourselves to-day for the service of the Lord, by preserving the obedience you have just shown towards Him, by not knowing either son or brother in His service, and thus gain for yourselves a blessing. In the fulfilment of the command of God, with the denial of their own flesh and blood, Moses discerns such a disposition and act as would fit them for the service of the Lord. He therefore points to the blessing which it would bring them, and exhorts them by their election as the peculiar possession of Jehovah (Num 3-4), which would be secured to them from this time forward, to persevere in this fidelity to the Lord. "The zeal of the tribe-father burned still in the Levites; but this time it was for the glory of God, and not for their own. Their ancestor had violated both truth and justice by his vengeance upon the Shechemites, from a false regard to blood-relationship, but now his descendants had saved truth, justice, and the covenant by avenging Jehovah upon their own relations" (Kurtz, and Oehler in Herzog's Cycl.), so that the curse which rested upon them (Gen 49:7) could now be turned into a blessing (cf. Deu 33:9).
John Gill Bible Commentary
And the children of Levi did according to the word of Moses,.... They girded their swords by their sides, went through the camp, and slew their brethren, companions and neighbours, who were keeping holy day in honour of the idol:
and there fell of the people that day about three thousand men; the Vulgate Latin version reads 23,000, very wrongly; now these being chiefly, if not altogether, of the tribe of Levi, the brethren, companions, and neighbours of the Levites, that were the slayers, together with the after plagues that came upon them, Exo 32:35 account for the deficiency of males in this tribe, some few months after, when it was numbered; and the number of them from one month old and upwards amounted but to 22,000, which was but a very small one in proportion to the other tribes, who generally, one with another, numbered 40,000 each, and none so few as 30,000 (r); of this tribe Aaron was, and therefore used with severity, because of his concern in this sin; and even though it was the tribe of Moses, it was not spared.
(r) See the Bishop of Clogber's Chronology of the Hebrew Bible, p. 360, 362.