Rashi recounts (on Bamidbar 8:2, from Tanchuma ch. 5) that Aharon experienced chalishas ha-da'as (dejection) for not having participated in the Chanukas Ha-Mishkan (Inauguration of the Mishkan), and that Hashem thereupon replied to Aharon that he should not feel bad, for his portion in the Mishkan was greater than that of the Nesi'im (Tribal Princes) who participated in the Chanukas Ha-Mishkan, because Aharon was to prepare and light the Menorah.

Why did Aharon experience dejection? Unlike the Nesi'im, Aharon was charged with all types of Avodah (Service) in the Mishkan every day. Hence, why did Aharon's exclusion from the one-time, voluntary inauguration of the Mishkan cause him distress? Furthermore, how was the mitzvah of the Menorah to be viewed as a just compensation or a preferred assignment so as to allay Aharon's feelings?

Aharon wished to be part of the Chanukas Ha-Mishkan due to its spontaneous, voluntary nature, as he could thereby serve Hashem with personal creativity rather than exclusively by routine command. Whereas Aharon's sons, Nadav and Avihu, were punished for performing Avodah based upon personal creativity, Aharon observed that Hashem made an exception to this ban by permitting the Nesi'im to bring spontaneous, voluntary korbonos as part of a procession which they initiated. (V. Rashi on Bamidbar 7:3.) Aharon thus felt that it was fitting that he, too, be privileged to be part of this one-time, unprecedented event.

Hashem responded to Aharon that "Your portion is greater than theirs", meaning that despite the pomp and circumstance of the Chanukas Ha-Mishkan, it did not measure up to Aharon's own Avodah. Whereas the Avodah of the Nesi'im was part of a one-time celebration, Aharon's Avodah constituted an eternal routine, and the sense of commitment to perform this routine day in and day out reflected an even greater level of devotion to Hashem.

This is where the Menorah comes in, as part of its mitzvah - if not the entirety of the Kohen's task with the Menorah - is to clean it out and prepare it for use. The Kohen must wipe the Menorah's oil holders clean and remove the used wicks, add fresh oil and insert new wicks every day. According to some Rishonim, the Menorah must be lit by a Kohen, whereas other Rishonim maintain that even a non-Kohen (a Zar) may light the Menorah, for the Kohen's role is merely to clean the Menorah and prepare it; lighting it is not part of his requirement. We see from this that the Kohen's mitzvah regarding the Menorah has a "janitorial" aspect to it, if one can use such crass terminology.

By commanding Aharon the mitzvah of the Menorah, Hashem affirmed that the Avodah which is most precious to Him is not that of grand performance and personal creativity. Rather, Avodah which reflects submissiveness and extreme humility is what Hashem seeks most. The Menorah embodies this type of Avodah, and it was thus the basis of Hashem's reply to Aharon's feelings of dejection.

The mitzvah of Terumas Ha-Deshen (Removal of the Altar's Ashes) is also an Avodah of lesser physical glory. Nevertheless, Hashem chose the mitzvah of the Menorah to convey the role of Aharon's Avodah and its import, for Chazal indicate (Menachos 86b) that the Menorah's light reflects the Shechinah, and Hashem was thereby imparting to Aharon and the Jewish People that service of submissiveness and humility is the true key to merit His Presence.