The laws regarding each of the thirteen different types of korbanos were exceedingly complex; where they were to be offered, how they were to be sacrificed, what else was brought with them [incense, libations et. al.]. Nevertheless, Aharon and his sons were able to fulfill the requirements with precision and as Rashi comments, this is their praise; they did not deviate at all from any of the instructions that Moshe gave. The Maharal [Gur Aryeh to Rashi], noting that the commandments were given by Moshe rather than directly by G-d, points out that lesser people might have resented Moshe’s insistence on precision. Aharon and his sons, however, accepted that Moshe was the messenger of G-d and they consequently were no less reluctant to heed his commands than they would have been willing to fulfill the commands had they been issued directly by G-d. In this sense, their actions are a lesson that we should all learn; not to resent authority, but to accept it [when it is validly applied and does indeed represent the will of G-d].
Throughout sefer Vayikra, we finds this idea being expressed; Aharon’s ability not to deviate or change the instructions of Moshe. Aharon’s ability to subjugate his own feelings and understanding of a situation is a remarkable lesson in self-discipline and in true anavah - humility. As we have noted elsewhere, Netziv comments that it is part of human nature to try to make our own imprint, to even take G-d’s commands and try to improve upon them. This is the root of the sin of the nazir, who for very valid reasons [his fear that he lacks self-control] takes upon himself obligations [refraining from drinking wine and coming into contact with a corpse] that the Torah does not demand. He is termed a choteh - a sinner - for his actions and must offer a sacrifice.
There is an old story taught about a writer who decided to translate Shakespeare into Yiddish. Asked for the title of his work, he replied: “Shakespeare fargressert und farbessert” [Shakespeare, expanded and improved]. If it is natural for us to try to improve upon the classics of literature, is it not natural for us to try to improve upon the ways of G-d? Are we not all experts in the will of G-d - perhaps even greater experts than G-d himself?
We find a similar attitude regarding some of the events surrounding Purim. Mordechai, the leader of Shushan Jewry, exhorts his fellow Jews to distance themselves from the celebrations arranged by Achashverosh, but his remonstrations fall on deaf ears. His fellow Jews feel that they are more astute observers of Persian politics and ignore the pleas of Mordechai. He is afterall, only a member of the Sanhedrin. What does he know or understand about real politics? It is only da’as Torah, they argue, nothing they need take seriously.