''Moshe then said to Aharon: ''Draw near to the altar'' [Shemini 9:7]
Rashi explains that Aharon was embarrassed and afraid to approach the altar. Moshe therefore said to him ''Why are you embarrassed? This is what you were selected for.''
The Baal Shem Tov elucidated Rashi's words. Moshe was saying to Aharon: Why are you embarrassed? It is specifically due to the fact that you possess the character trait of humility and that you feel ashamed before Hashem that you were chosen to be the Kohen - ''This is what you were selected for!"
Source: Rabbi Yisrael Bronstein