Musar sobre Números 16:1

Jealousy caused Korach to "robe himself" in haughtiness, caused him to aspire to greatness. This is why the expression ויקח קרח, should be understood as "he took the fact that he was the son of Yitzhar into consideration, and decided he was entitled to higher rank than had been accorded him so far. We know that Bamidbar Rabbah quotes Rabbi Levi as saying that Korach considered the fact that he was the son of יצהר, [another name for oil], and that oil always floats on top. Furthermore, he considered the fact that he was also the grandson of Kehat who had been found worthy to found the family that would carry the Holy Ark. By dwelling on these points he convinced himself that the position of leadership of the Kehatites should have belonged to him, and not to Elitzafan who was only fourth in line. These were the considerations which resulted in his being deprived of his life and his future.