In his commentary on Numbers, Michael Morales points out some important parallels between Numbers 16 and Genesis 4. In both chapters, a firstborn son is jealous of a relative, feeling slighted over a matter of worship.
In Genesis 4, Cain is jealous of his brother Abel after Abel presents an acceptable sacrifice (Hebrew minchah) to God and Cain presents an unacceptable one.
In Numbers 16, Korah is jealous because he has been passed over for the priesthood, the leadership of the clan of Kohath, and leadership of Israel. Genealogical information in Exodus 6:16-22 supports this conclusion. We see in Exodus 6 that Aaron was the first son of Kohath's firstborn son Amram, while Korah was the first son of Kohath's second son Izhar. But Elzaphan, second son of Kohath's fourth son Uzziel, was placed over the clan of Kohath in the Israelite camp instead of Korah (Nu 3:30).
One striking verbal parallel between the Genesis 4 and Numbers 16 involves the ground "opening up." In Genesis 4:11, the ground opens up to receive the blood of Abel, who has been murdered by Cain. In Numbers 16:32, the ground opens up to swallow a group of rebels that may include Korah (see also Num 26:9-10).
The parallels between Numbers 16 and Genesis 4 may help explain Numbers 16:15, where Moses prays, "Do not respect their offering," referring to Korah and the group of 250 leaders he represents. In this verse, the Hebrew word for "offering" is again minchah, as in Genesis 4:3-4. Moses recognizes in Korah and his followers the jealous, murderous spirit of Cain, and so he believes that Korah's offering, like Cain's, should not be accepted.