Numbers 17:6

But on the following day the whole congregation murmured against Mosheh and Aharon, saying: You have been the occasion of the judgment of death against the people of the Lord.

YE HAVE KILLED THE PEOPLE OF THE ETERNAL.’ Onkelos rendered it: “You have caused the death of the people of the Eternal.” Thus he interprets the verse [to mean that] the people accused Moses and Aaron that because they advised Korach and his company to offer up strange incense to G-d of their own accord, those who offered it up were burnt, since G-d had not told Moses to offer up this incense, nor did he tell Israel to do so in the name of G-d; thus they of their own accord proposed this matter as a result of which the people died — when they could have [just as well] given another sign or miracle, through the rod, or [through] some other [harmless] test.
And Rabbi Abraham ibn Ezra said [that the verse means that the people said]: “What proof is this that the tribe of Levi has been chosen, and that Aaron was chosen to be the High Priest? It is possible that by your prayer or by some [secret] wisdom which you possess you burnt those that offered the incense.” [All this is the language of Ibn Ezra]. And so indeed it appears, that they did not yet believe [in the Divine selection of the tribe of Levi], for when He stated afterwards, Speak unto the children of Israel, and take of them rods, one for each fathers’ house; And it shall come to pass, that the man whom I shall choose, his rod shall bud, and I will make to cease from Me the murmurings etc., Verse 20. — this proves that the people did not [yet] believe, as a result of the fire, that the Levites were chosen [for service in the Sanctuary] and that the firstborn had been exchanged for them, but they thought that Moses and Aaron had caused the fire [of their own accord]. Or [it may be that the people thought] that the punishment came because they burnt the incense with strange fire which He had not commanded them, and [that Aaron was saved because] Aaron’s incense was the [daily] incense of the morning [commanded by G-d], as I have explained. [According to this interpretation] the complaint [of the people] was only about [those two hundred and fifty men who offered the incense and who were consumed by] the fire,, Verse 35. but not about those men [Korach, Dathan, and Abiram] who were swallowed up by the earth,, Verse 32. for G-d had said to Moses, Get you up from about the dwelling of Korach, Dathan, and Abiram,, Verse 24. and this alluded to the opening of the mouth of the earth. Moses had told this to Israel in the name of G-d. Furthermore, Dathan …

'אתם המתם את עם ה, they meant that while they agreed that Datan and Aviram having been swallowed up by the earth as being an appropriate punishment for them, they did not see why the 250 men with them who had offered incense deserved the same fate.

'אתם המתם את עם ה, by telling all these people to test G’d by offering incense, something that is only fit to be offered together with the public burnt-offering burned on the altar every day in the morning and evening by the individual priest performing that service. If you wanted to make such a test you should have done so with meat offerings, a procedure in which a large number of priests can participate.

'אתם המיתם את עם ה, “you (Moses and Aaron) have killed the Lord’s people!” The people accused Moses and Aaron as having done this knowingly, as they knew telling them to offer incense outside the sacred soil of the Tabernacle would result in their death. After all, Nadav and Avihu who had been anointed as priests, as opposed to the 250 men Moses told to offer incense had been killed on the spot for doing so in the wrong place and at the wrong time. Moses told Aaron to take the fire-pans that had served these 250 men as the base for their incense and to demonstrate that it was not the incense nor the pans in which it had been offered that killed people but that it was their sins which killed them. When the people heard this, they replied that this was no proof, as they may have died seeing that they were not worthy of becoming priests. G–d therefore ordered Moses to take staffs from each of the leaders of the tribes of Israel and to place them side by side inside the Tent of testimony, (Tabernacle) each staff belonging to the respective leader of their tribe, (verse 17) [people whom they considered most worthy, Ed.]) In this way, from the results of this test, G–d hoped to silence the people’s complaints about nepotism once and for all. (verse 25)