Subsequent to the death of Nadav and Avihu, Aharon’s sons, Aharon approaches Moshe and asks him if he is able to bring the Korban offerings; since, as Kohen Gadol, he can perform the Avodah even during the highest level of Aveilut, mourning, as an Onein, someone who has lost a close relative and has yet to bury them. The Passuk states, “VaYiShma Moshe VaYiTav BeEinav.” “And when Moshe heard that, it was agreeable to him” (VaYikra 10:20). Rashi explains that Moshe was admitting here that he had not heard this Halacha and that Aharon’s ruling was correct.
The Gemara (Zevachim 101a) asks, why did Moshe tell the truth about his lack of knowledge of this Halacha? He could have easily lied and said that he knew the Halacha. Furthermore, the Midrash says Moshe went beyond admitting he didn’t know this Halacha to Aharon, and told all of Bnei Yisrael that he had forgotten the Halacha. This seemingly reasonless and unnecessary admission creates a potential problem. Moshe announcing that his knowledge of Torah is not complete gave the Bnei Yisrael a reason to doubt whether or not he was really receiving the Halachot from Hashem. Additionally, even if he did receive the Halachot from Hashem, if he had forgotten one, how many more did he potentially forget?
We may answer that not only did Moshe make the right decision by announcing his mistake; he even strengthened Bnei Yisrael’s belief in his transmissions from Hashem by showing that it really is the word of God and not his own, and therefore he is able to forget what was told to him. This is illustrated by the countless times that Moshe is referred to as an Eved Hashem in Neviim. Moshe is referred to in this manner because he acted like a slave to Hashem. Just as a slave owns nothing, as it is entirely his master’s, so too Moshe did not take credit for anything that came from Hashem.