Rashi states that the Torah is teaching and praising the level of Aharon HaKohen’s and his sons’ commitment. “They did not deviate ‘right or left’” from all that they were commanded, and did exactly as instructed despite the voluminous details and minutae involved in these laws. Sifra comment that this alludes not only to their execution of the mitzvah, but also to the joy inherent in their performance. Although they did not hear the command directly from Hashem, Aharon and his sons performed it with enthusiasm and zest. There was no volunteering someone else, shrugging of shoulders, or exhibiting false modesty. They were told and immediately accepted without fanfare.
The Chasam Sofer, zl, asked one of his congregants to lead the tefillah, services. The congregant responded atypically, presenting a side of humility heretofore unknown to anyone. He shrugged his shoulders, as if to say that he was unworthy of such a distinguished honor. The Chasam Sofer countered, “The Torah teaches that, ‘Aharon and his sons carried out all the matters.’ Rashi explains that Aharon and his sons listened without deviating to the right or left. This means that they did not shrug their shoulders in ‘humility.’ They did not present themselves as being unworthy. They were told to do something, and they did it!” Excessive humility is a subtle form of arrogance.
