Why Aharon Was Chosen
Humility
Moshe told Aharon to draw near to the Mizbeach, and Rashi explains that Aharon was ashamed and held back. Moshe asked why he was ashamed, for this was why he had been chosen. The Degel heard from the Baal Shem Tov that this is not a question about why Aharon felt shame, but a statement of the reason Aharon was chosen: his fear and humility were exactly what Hashem desires. The Degel adds that the Hebrew words for fear and shame combine to spell Bereishis, which can also read as a reference to how fortunate Aharon was to be chosen to serve the Daughter of the King, the Shechinah.
Source: Degel Machaneh Ephraim, Shemini