In this Parshah we read about a sad but important story that occurred while the Jewish people were in the desert. Some jealous, evil people tried to challenge Moses' leadership, and the disastrous results taught all the Jews an important lesson.

Korach, after whom the Parshah is named, is from the tribe of Levi, so he has the honor of helping the Kohanim and carrying the parts of the Mishkan while traveling. But for him this isn't enough; he is jealous of Aaron because he wants to be a a Kohen too. So he gets a bunch of people to be on his side—Dathan and Aviram, the usual troublemakers, On, the son of Peleth, and two-hundred and fifty others—and goes to complain to Moses and Aaron, saying. "Why should you two be the leader and the Kohan? Isn't every Jew special? Why do you think you're better than everybody else?"

In order to prove that they really are worthy of being Kohanim, Korach and his men prepare an offering of Ketoret to bring in the Mishkan. Aaron also prepares an offering, and they all stand outside the Mishkan holding their pans. Suddenly, the earth opens and swallows those rebelling against Moses—Korach, Dathan, and Aviram—and a fire comes out and consumes all the 250 men who are trying to bring a ketoret.

All of the Jews watch the scene, and it is clear to everybody that Moses is the true leader, appointed by G‑d, and that only a Kohen—Aaron or his sons—is allowed to bring the ketoret offering. But then some of the still Jews complain, so a plague begins to spread. Aaron rushes to bring a ketoret offering as an atonement for the people and the plague stops.

G‑d makes one more miracle to prove that Aaron's family are the only true Kohanim. Aaron's staff—the dry stick he would carry with him—miraculously starts growing almonds. When everyone sees this dead stick suddenly sprouting, it is clear that Aaron is the Kohen chosen by G‑d.