Moshe and the elders of Israel commanded the people, saying, "Keep all the commandments which I command you this day.
The Ohr Hachaim explains this possuk based on a Gemara. The Gemara tells us that when the matter concerns Chillul Hashem, no honor is due to the Rav. This is based on a possuk in Mishlei אֵין חׇכְמָה וְאֵין תְבוּנָה וְאֵין עֵצָה לְנֶגֶד ה' - There is no wisdom nor understanding nor counsel against Hashem. This is taken to mean that there is no respect for wisdom or understanding when the honor of Hashem is at stake.
Usually, Moshe Rabbeinu did everything himself; we do not find him bringing the Elders of Klal Yisroel with him. Indeed, it would not be honorable for his Torah for him to share the position with others.
However, these pessukim are discussing the curses that will befall those who desecrate the terrible aveiros enumerated. The possuk uses the word שמר – guard, which is usually applicable to the Torah’s prohibitions. In this case, there is no place to make sure to honor Moshe Rabbeinu, and it is more important to uphold the Torah.
This is why Moshe chose the elders to stand alongside him. He wished to teach Klal Yisroel that when dealing with these terrible aveiros, there is no place for honor and respect for those who may be wiser than yourself. Everyone has to protest, regardless of other people’s honor.
