Aharon had certain responsibilities as the Kohen Gadol. In the opening verses of the Portion Shemini we read of some of the functions given to Aharon. Then the Torah tells us that Moshe said to Aharon: וַיֹּאמֶר מֹשֶׁה אֶל אַהֲרֹן קְרַב אֶל הַמִּזְבֵּחַ וַעֲשֵׂה אֶת חַטָּאתְךָ וְאֶת עֹלָתֶךָ, “Moshe said to Aharon: Come near to the Altar and perform the service…” (Lev. 9,7) Rashi states: Aharon was ashamed and feared to go there.
There is a very significant lesson to be learned here. Aharon was given instructions and he hesitated to perform his duties for fear of approaching the Altar. Rabbi Moshe Tzvi Neria, one of the founders of the Bnei Akiva youth movement, in his volume on the Torah writes in connection with a different verse a very cogent argument for following instructions.
He points out that when a commander in a war gives a charge to his soldiers to perform a certain operation, they must obey without hesitation. If they feel they must understand every comment and worry about every act if it is safe, then that army would certainly lose the war.
This can be applied to Aharon. He was given instructions by the Almighty and he had to obey them.
This reasoning can also be applied to Mitzvot that we cannot understand. As believers in our Torah we must be willing and ready to perform all commandments even though we do not understand their rational.