One of the simple tasks that the Kohanim were asked to do, was the removal of the ashes on the altar. This was called, תרומת הדשן.
After the offering of numerous sacrifices, there would be an accumulation of ashes that needed to be removed. Although this seemed to be a very menial task, the Kohanim performed it with great zeal and enthusiasm.
The Torah makes a point of telling us that the Kohanim must also wear their holy priestly garments, when performing the Mitzva of תרומת הדשן.
The message here is that we are to perform all Mitzvot in a dignified manner. It could even be reflected by the manner in which we dress when we pray. We should feel fortunate we are able to perform service of Hashem. We must learn from the Kohanim to do every service with enthusiasm and dignity.