Why Nadab and Abihu Died After Coveting Moses and Aaron

Midrash Tanchuma Buber, Achrei Mot 13:1

[From where came the offense for which they received [what was theirs]? Rabbi Hoshaya said: When Moses was going up, and the elders of Israel with him, from the wilderness, Aaron and Hur and seventy elders and Nadab and Abihu were going up with him. Moses and Aaron were walking first, Nadab and Abihu walking after them, and all the elders of Israel walking after them. And Nadab and Abihu were musing in their hearts, and they said: When will these two elders depart, so that we may take authority and we ourselves be first in every matter? The Holy One, blessed be He, said to them (Proverbs 27:1): "Do not boast about tomorrow." Many colts have died, and their hides have been made into coverings upon the backs of their mothers. He said to them: From that hour you deserved to receive what was yours; but what shall I do? Behold, I am waiting for you until the Tabernacle is set up, and after that I shall judge you. Therefore, when the Tabernacle stood, they received their sentence and died, "after the death of the two sons of Aaron" (Leviticus 16:1).]

Themes

Biblical References