John Gill Commentary Exodus 6:21

"And the sons of Izhar: Korah, and Nepheg, and Zichri." — Exodus 6:21 (ASV)

And the sons of Izhar, Korah, and Nepheg, and Zichri .
] These seem to be mentioned for the sake of Korah, concerning whom is a remarkable history in the following book; for the other two are nowhere else spoken of.