The first Mishnah in Pirkei Avot teaches: “Moshe received the Torah from Sinai and passed it on to Yehoshua.” It would seem more correct, however, to state that Moshe received the Torah from Hashem, for Mount Sinai did not give the Torah to Moshe, for it does not seem that this is the correct place to mention the geographic location of the giving of the Torah; rather, it should record who the Torah was given to Moshe by, as the Mishnah continues, “And he [Moshe] passed it on to Yehoshua and Yehoshua passed it on to the elders.”
Maran zt”l explains this concept based on the words of our Sages in the Midrash which states that when Hashem wished to give the Torah to the Jewish people, various mountains raced and clashed with one another each claiming that the Torah would be given on itself (obviously, this does not mean that the mountains themselves clashed, for mountains are inanimate objects; rather, this means that the angels appointed over these mountains very much wished that the Torah be given on the specific mountain in their charge). Mount Tavor came from Bet Elim and Mount Carmel came from Spain, each wishing for the opportunity for the Torah to be given on it. Hashem told them, “Why do you quarrel with Mount Sinai? Do you not know that you are all considered blemished relative to Mount Sinai?” This means that Hashem considered all of the haughty mountains “blemished.” Mount Sinai which was humble, for it was the lowest of all mountains, was considered “unblemished” with regards to the other mountains. Rav Ashe learned from here that an arrogant person is considered “blemished.”
Based on this, we can understand the answer to the above question regarding the wording of the Mishnah, “Moshe received the Torah from Sinai,” which is actually hinting to the reason why Moshe Rabbeinu and no one else merited receiving the Torah on Mount Sinai. This is what the Tanna meant by writing that Moshe received the Torah “from Sinai,” meaning that just like Mount Sinai merited that the Torah was given on it because of its humility and lowliness, Moshe Rabbeinu merited receiving the Torah for the same reason, i.e. because of his extreme humility. Indeed, the Torah attests to this fact by stating, “And the man Moshe was very humble, more than any other man on the face of the earth.” The Midrash explains that the words “More than any other man” refer to the fact that he was so humble that he would not grow haughty due to any reason other people may become arrogant as a result of, such as wisdom, prophecy, or sovereignty. Although Moshe encompassed all of these traits, he was nevertheless the humblest man on the face of the earth. For this reason, when Moshe told Hashem, “Who am I that I should go to Pharaoh,” Hashem replied, “Here is a sign for you that I have sent you,” meaning that this is exactly the reason I am sending you and no one else, because you belittle yourself.
The reason why Hashem considers specifically arrogant people to be blemished as opposed to people with other destructive character traits is because most people possessing other bad character traits are not in as bad a state as a haughty individual, for if someone has an anger issue, it is quite easy for the individual to realize that he has a short fuse. Similarly, a miser will soon realize that it is more difficult for him to part with his money than his friends. On the other hand, an arrogant individual can live out his entire live without realizing the terrible character flaw he possesses. One must therefore guard himself so that one does not fall into this destructive trap called “arrogance,” for Hashem cannot bear an arrogant person, as the verse states, “Hashem’s aversion is one haughty of heart.” However, a humble person is extremely beloved by Hashem, for this is the very attribute for which Moshe Rabbeinu merited receiving the Torah which formed us into a great nation.