Musar sobre Malaquías 3:22

Also, from the Great Din, of which it is written (Malachi 3:19): "For, behold, the day is coming which will burn as an oven" — one who occupied himself with Torah is destined to be rescued, as we find in Midrash Tehillim: "In time to come, the Holy One Blessed be He will take the sun out of its case and judge [i.e., punish] with it the wicked, and heal with it the righteous, as it is written (Ibid. 20): 'And there shall shine for you, fearers of My name, the sun of charity with healing in its wings, etc.'" R. Yehoshua said: "The Holy One Blessed be He did charity with all who enter the world by not having placed it [the sun] in the first firmament. For if he had placed it there, there would be no shade for anyone under it, as it is written (Psalms 19:7): 'And there is no hiding from His sun.'" But in time to come, who is hidden from His sun? He who occupies himself with Torah, as it is written afterwards (Ibid. 8): 'The Torah of the L-rd is complete.'" And the verse (Malachi 3:19): "For, behold, the day is coming which will burn like an oven" is, likewise, followed by (Ibid. 22): "Remember the Torah of Moses, My servant."

Now, from this we can learn from the minor to the major. If it is not worth delaying the redemption of all Israel by a single minute, what could we say if our righteous Moshiach comes and tells us, in HaShem’s Name, to offer the sacrifices that are on behalf of the entire Jewish people and the sacrifices specified in the book of Ezekiel, and at the very least, we will have to wait several weeks or months until we are proficient in them!?¹³Authors note: A person should not say to himself that when Moshiach and Eliyahu come, they are destined to clarify for us matters in which we have doubt. This is as stated in various places in the Talmud regarding various matters in which we have doubt, using the word “Teiku-תיקו,” regarding which the commentators said that this is an acronym for “[Eliyahu the] Tishbi will answer questions and difficulties-Tishbi Yetaretz Kushiyot U’Ba’ayot-תשבי יתרץ קושיות ואבעיות.” If one posits this, we will answer him that although it is true that all matters in which there is doubt will become clarified for us by Eliyahu, nevertheless, the simple matters that are stated in the verses or the explanations of the Torah that we have received as an Oral tradition, that have been passed down to us, and which are explained in Torat Kohanim [Leviticus] and in the Talmud, we ourselves must know them according to the maximum of our abilities. For, Eliyahu will not come to learn with each individual and teach him matters that he is able to know on his own, but will solely come to clarify and remove doubts in matters that we are unable to understand on our own. However, when it comes to simple matters that are expressly stated and can be understood on our own, he will tell us, “Why did you not study and learn them on your own before my arrival to announce the redemption, as it states (Malachi 3:22), ‘Remember the teachings of My servant Moshe, which I commanded him at Chorev, for all of Israel – its decrees and its statutes,’ and only in the next verse does it state, ‘Behold, I send you Eliyahu the prophet before the coming of the great and awesome day of HaShem etc.’”

The Ran proceeds to answer this question at length. What he says in essence is that Moses' speech defect was a necessary component of his very greatness. The Torah is called תורת משה; had Moses had a perfect command of speech, the greatness of Torah would not have become evident because people would have attributed the brilliance of the Torah's thoughts to Moses' eloquence. We all know that orators by their presentation can make mediocre content appear brilliant.