Korah, the leading spirit in this movement, was a Levite, of the family of Kohath, and a cousin of Moses; he was a man of ability and influence. Though appointed to the service of the tabernacle, he had become dissatisfied with his position and aspired to the dignity of the priesthood. The bestowal upon Aaron and his house of the priestly office, which had formally devolved upon the first-born son of every family, had given rise to jealousy and dissatisfaction, and for some time Korah had been secretly opposing the authority of Moses and Aaron, though he had not ventured upon any open act of rebellion. He finally conceived the bold design of overthrowing both the civil and the religious authority. He did not fail to find sympathizers. (Patriarchs and Prophets, 395)
Reflection: So often we get jealous of others and think we have the same right as they have. Korah had tremendous abilities. In his own eyes he felt more capable than Aaron and his sons. With God, it's not all about capabilities, but how and wow should perform the duties. If we will do it God's way and trust in Him, we will be developing a most important part of our characters.