After months and months of preparation the mishkan was about to be open for business. Aharon, the High Priest was about to begin the ceremonial inauguration when the demons of his past emerged
…וַיֹּ֨אמֶר מֹשֶׁ֜ה אֶֽל־אַהֲרֹ֗ן קְרַ֤ב אֶל־הַמִּזְבֵּ֙חַ֙
Then Moses said to Aaron: “Come forward to the altar…”
Aharon, explains Rashi, needed to be encouraged to begin the service because he was paralyzed with fear
|Aaron was embarrassed and feared to go there. Moses therefore said to him “Why are you embarrassed? For this purpose you have been chosen!”||שֶׁהָיָה אַהֲרֹן בּוֹשׁ וְיָרֵא לָגֶשֶׁת, אָמַר לוֹ מֹשֶׁה, לָמָּה אַתָּה בוֹשׁ? לְכָךְ נִבְחַרְתָּ|
Rashi is quoting a Midrash which sheds even more light onto Aharon’s state of mind
An analogy: A king married a woman and she was ashamed in his presence — whereupon her sister came in to her and said: Why did you agree into this? Is it not only for the sake of ministering to the king? Embolden yourself and serve the king! Similarly, Moses says to Aaron: My brother, why were you chosen as high-priest? Is it not only for the sake of ministering before the Holy One Blessed be He? Embolden yourself and perform your service! Others say: Aaron perceived the (horned) altar as an ox and was frightened by it (because of his sin with the Golden Calf), whereupon Moses said to him: My brother, don’t be afraid — “Draw near.” Embolden yourself and draw near to Him.
The Midrash gives us a clear picture of Aharon’s fear and Moshe’s encouragement. Aharon thought he was unworthy to serve God. Moshe tells him that serving God isn’t about how worthy you are. It isn’t an honor to serve God! True service is about God, not you! It doesn’t matter how “worthy” we feel so long as we make sure that what we are doing is God-centric.