ויהי ביום השמיני קרא משה לאהרן ולבניו ולזקני ישראל
Rashi explains that, when Moshe Rabbeinu summoned Aharon, he also asked the zekeinim, elders, to join them. It was important for the zekeinim to hear/see that Al pi haDibur Aharon nichnas u’meshameish b’Kehunah Gedolah, v’lo yomru meieilav nichnas, “In accordance with the statement (dibur) of G-d, Aharon enters and officiates in the office of Kehunah Gedolah, and they should not say he enters the office of Kehunah Gedolah on his own.” Apparently, Moshe Rabbeinu was concerned that the people would criticize the appointment of Aharon HaKohen as Kohen Gadol. Thus, he underscored that it was al pi haDibur, by Hashem’s…