Why did God regard the people's complaints after the results of the "ketoret test" as such a grievous sin?
Parashat Korach tells of God's miraculous intervention to foil the attempt by Korach and his followers to challenge the authority of Moshe and Aharon. Korach's two hundred and fifty cohorts who demanded the right to the priesthood were consumed by fire when they brought an incense offering, and Datan and Aviram, the other prominent leaders of the revolt, were devoured by the ground.
Immediately following this incident, Benei Yisrael approached Moshe and Aharon and cried, "You have killed the congregation of the Lord!" (17:6). God responded very harshly to this accusation, declaring to Moshe and Aharon, "Move away from amidst this nation, and I will destroy them in an instant" (17:10). Moshe ordered Aharon to bring a special incense offering to atone for the people, and Aharon's gesture succeeded in ending the plague only after the tragic death of 14,700 members of Benei Yisrael.
Why did God regard the people's complaints as such a grievous sin, deserving of a harsh, deadly response?
Several classic commentators explain that the people questioned the legitimacy of the "ketoret test" that Moshe had conducted. Recall that upon hearing the demand of Korach's followers for the rights to the priesthood, Moshe invited them to offer incense together with Aharon the following morning to determine whom God had selected for the role of kohen. Aharon, of course, emerged unscathed, whereas Korach's two hundred and fifty followers were consumed by fire. The Rashbam and Seforno thus explain that the people now accused Moshe of deliberately killing Korach's followers by instructing them to offer incense. Ibn Ezra explains somewhat differently, arguing that the people were unconvinced by the results of the ketoret offering. They accused Moshe and Aharon of "manipulating" the results through prayers or some kind of mystical powers, such that the death of the two hundred and fifty rebels did not prove their exclusion from the priesthood.
According to Ibn Ezra's approach, we can perhaps more clearly understand the Almighty's response. Essentially, the people here continue the campaign led by Korach against Moshe and Aharon. They rejected the "ketoret test" and insisted that Moshe and Aharon had no right to deny the rest of the nation the privileges of the kehuna. This incident is simply the continuation of Korach's revolt, to which God had initially responded by announcing to Moshe and Aharon, "Separate from this nation, and I shall destroy them in an instant!" (16:21). Moshe and Aharon had quelled God's fury by rhetorically asking, "Shall one person sin – and you will be angry at the entire nation?" (16:22). But now, after the deaths of the leaders of the revolt, as the people persistently sought to perpetuate their campaign and their legacy, the revolt could no longer be attributed to a small handful of agitators. God therefore repeats (almost verbatim) his warning: "Move away from amidst this nation, and I will destroy them in an instant!"
Rav Shimshon Refael Hirsch explains in a slightly different vein. Like Ibn Ezra, Rav Hirsch explains Benei Yisrael's complaint as a rejection of the "ketoret test." In his view, however, the people claimed not that Moshe had manipulated the results through some magical intervention, but rather that the deaths could have been averted had Moshe and Aharon reacted more indulgently to the challenge to their leadership:
They still imagined…that the election of Aaron, admittedly at God's behest, nevertheless rested more as a personal distinction conferred on the brother of Moses. So that they took the sin of the two hundred and fifty as being punished by God for the personal insult to Moses and Aaron, which they thought could have been averted by Moses and Aaron forgiving this insult, and so they could – and should – have prevented the death of such a considerable number of fathers and families.
Benei Yisrael conceded that the incense offering proved God's selection of Aharon, but they viewed it as God's defense of Moshe and Aharon's honor. Had Moshe and Aharon been less concerned with their personal status of honor, they charged, the tragedy would have been avoided.
Rav Hirsch proceeds to explain on this basis God's response to the people's accusations: "Move away from amidst this nation, and I will destroy them in an instant." As the people had launched a personal attack against Moshe and Aharon, God offered to destroy the nation. But Moshe and Aharon demonstrated their genuine love for and loyalty to the people by quickly acting on their behalf to atone for their sin, despite the harsh accusations they had made against their devoted leaders.
Courtesy of Yeshivat Har Etzion - www.etzion.org.il