Based on this introduction, we will proceed to explain why HKB”H specifically chose the two holy brothers—Moshe and Aharon—for the task of taking Yisrael out of Mitzrayim. For, upon closer scrutiny, it is apparent that Moshe and Aharon occupied themselves with these two aforementioned categories. Moshe Rabeinu dealt almost exclusively with connecting Yisrael with their heavenly Father. This was evident when he said to Yisrael (Devarim 5, 5): "אנכי עומד בין ה' וביניכם בעת ההוא להגיד לכם את דבר ה'"—I was standing between Hashem and you at that time, to relate the word of Hashem to you.
The Midrash (D.R. 11, 4) reinforces this notion beautifully in relation to the passuk (ibid. 33, 1): "וזאת הברכה אשר ברך משה איש האלקים. מהו איש האלקים, אמר רבי אבין, מחציו ולמטה איש, מחציו ולמעלה האלקים". The passuk depicts Moshe as “ish haElokim”—the man of G-d. The Midrash questions the meaning of this description. Rabbi Avin explains that his bottom half was man-like, while is upper half was G-d-like. In Tiferes Yisrael (Chapter 21), the Maharal of Prague provides us with an interpretation of this Midrash: Moshe was not merely the intermediary between HKB”H and Yisrael, having a connection with each side, but he occupied an intermediate status between the two—as the passuk states (Devarim 5, 5): "אנכי עומד בין ה' וביניכם"—I stand between Hashem and you. He belonged to both the earthly realm and the heavenly realm, as reflected by the description “ish haElokim.” Therefore, he was able to ascend and descend between earth and the heavens in order to receive the Torah from HKB”H and deliver it to Yisrael. Here are the sacred words of the Maharal:
"ומפני כי משה היה מן התחתונים ומן העליונים, כמו שאמרו שנקרא משה איש האלקים, מחציו ולמטה היה איש ומחציו ולמעלה היה אלקים, ולכך אי אפשר לומר רק שהיה כמו אמצעי בין העליונים ובין התחתונים, והאמצעי מצורף לשניהם, ולפיכך עלה שמים וירד, והיה למשה משפט האמצעי, שנאמר אנכי עומד בין ה' וביניכם להגיד לכם דבר ה' וגו'".
On the other hand, Aharon HaKohen dealt almost exclusively with establishing and maintaining shalom among the members of Yisrael. This is apparent from the following passuk (Bamidbar 20, 29): "ויראו כל העדה כי גוע אהרן ויבכו את אהרן שלשים יום כל בית ישראל"—the entire assembly witnessed that Aharon had perished; they wept for Aharon thirty days—the entire house of Yisrael. Rashi comments: Everyone grieved over Aharon’s death, both men and women alike, since he was the ultimate peacemaker—he promoted shalom and amity among disputants, and between husbands and wives.
Similarly, the Mishnah states (Avos 1, 12): "הלל אומר, הוי מתלמידיו של אהרן, אוהב שלום ורודף שלום, אוהב את הבריות ומקרבן לתורה"—Hillel says: Be among the disciples of Aharon—love peace and promote peace, love your fellow creatures, and bring them closer to Torah. The method employed by Aharon HaKohen is described in Avos D’Rabbi Nasan (12, 3). Here is a loose translation:
If two people were quarreling, Aharon would go sit down with one of them and say to him, “My son, see what your friend is saying. He is heartbroken and is ripping up his garments. He is saying, ‘Woe is me; how can I go face my friend? I am ashamed to face him, since I have insulted him.’” He (Aharon) would sit with him until he removed the jealousy from his heart. Then, Aharon would go and sit with the other one. He would say to him, “My son, see what your friend is saying. He is heartbroken and is ripping up his garments. He is saying, ‘Woe is me; how can I go face my friend? I am ashamed to face him, since I have insulted him.’” He (Aharon) would sit with him until he removed the jealousy from his heart. Thus, when they bumped into each other, they embraced and kissed one another. Therefore, it says, “They wept for Aharon thirty days—the entire house of Yisrael.”
Based on this, it is easy to comprehend why Aharon HaKohen merited the privilege of having Birkas Kohanim given to him and his descendants. After all, Birkas Kohanim concludes with the berachah of shalom (ibid. 6, 26): "ישא ה' פניו אליך וישם לך שלום"—may Hashem lift His countenance toward you and bring you peace. Now, we have a basic principle taught in the Gemara (B.M. 107b): "קשוט עצמך ואחר כך קשוט אחרים"—first correct yourself and only afterwards correct others. Therefore, there is no one more fitting than Aharon HaKohen to bestow the berachah of shalom upon Yisrael. For, he spent his entire life promoting shalom—among friends and among husbands and wives.
