Numbers 14:37

In a plague, before Adonoy. By the particular death suited to them, measure for measure. They sinned with the tongue, so their tongues were distended until their navel, and maggots came from their tongues and entered their navel. This is why it says, בַּמַּגֵּפָה, and not בְּמַּגֵּפָה . And this is [the meaning of] “before Hashem” — as particularly suited to them, according to the attributes of the Holy One, Blessed is He, Who metes out measure for measure.

(even those) men who had brought forth the evil of the report of the land died, on the seventh day of the month of Elul, with worms coming from their navels, and with worms devouring their tongues; and were buried in death from before the Lord.

AND THOSE MEN, THAT DID BRING FORTH ‘DIBATH’ (AN EVIL REPORT) OF THE LAND, DIED. I have already explained that their severe punishment was because of the report which they spread that it is a Land that eateth up the inhabitants thereof, which was a complete falsehood since the Land was full with many people, as it is written in the Book of Joshua, And they went out, they and all their hosts with them, much people, even as the sand that is upon the sea-shore in multitude, with horses and chariots very many. And in the Torah it is written, and He shall cast out many nations before thee … seven nations greater and mightier than thou. The spies also emphasized the strength of the people, saying: the people are fierce, and they are very strong,, Verse 31: for they are stronger than we. and did not report back concerning the words of Moses who told them [to ascertain] whether they are few or many,, Verse 18. but they told the people afterwards that the Land is one that eateth up the inhabitants thereof!
Now Rashi commented: [the spies] made all the congregation to murmur against him by bringing forth ‘dibah’ against the Land. “Whenever Scripture uses the expression ‘he brings forth dibah’ it means bringing forth words which ‘capture’ a person so that he speaks about it, just like ‘doveiv’ (stirring) the lips of those that are asleep. And [the expression ‘bringing forth dibah’] may be for good, or for evil. That is why it says [the men … that did bring forth an “‘evil’ dibath” (report of) the Land], because there may be a dibah which is good.” [Thus far is the language of Rashi.] But it is written: he that bringeth forth ‘dibah’ is a fool, and this cannot [refer] to a good [utterance]. Similarly, bringing forth ‘dibah’ against the Land, and so also, ‘v’dibathcha’ (and thine utterance of ‘dibah’) he will not turn away — all signify speech of evil, as the term dibah itself connotes evil, and when Scripture uses the expression dibah ra’ah [“evil dibah,” as it does in our verse: and those men that did bring up ‘dibath ha’aretz ra’ah’ (an evil report of the Land) died] it is to emphasize the greatness of the evil that they did.

וימותו האנשים מוציאי דבת הארץ רעה במגפה, from the type of pestilence which they claimed had caused the death of the people they had seen dying in the land of Canaan during their tour of exploration. (13,32) It was the kind of pollution in the air which kills almost instantly.