וַיִּבְכּוּ֩ בְנֵ֨י יִשְׂרָאֵ֧ל אֶת־מֹשֶׁ֛ה בְּעַֽרְבֹ֥ת מוֹאָ֖ב שְׁלֹשִׁ֣ים י֑וֹם וַֽיִּתְּמ֔וּ יְמֵ֥י בְכִ֖י אֵ֥בֶל מֹשֶֽׁה׃
Und die Kinder Israel weinten dreißig Tage lang in den Ebenen Moabs um Mose. So endeten die Tage des Weinens in der Trauer um Mose.
Rashi on Deuteronomy
בני ישראל THE CHILDREN OF ISRAEL [WEPT] — i.e., the men; but regarding Aaron, — because he pursued peace, and made peace between a man and his fellow, and between a woman and her husband, it is stated, (Numbers 20:29) “The whole house of Israel [wept for him]” — the men and the women (Pirkei DeRabbi Eliezer 17).
Sforno on Deuteronomy
ויתמו ימי בכי אבל משה ויהושוע בן נון מלא רוח חכמה, for during the days of weeping for Moses there was neither wisdom nor counsel (חכמה ועצה).
Or HaChaim on Deuteronomy
ויבכו בני ישראל, The Jewish people wept, etc. When Aaron's death is reported in Numbers 20,29, the Torah wrote that "the whole house of Israel wept for thirty days." Our sages in Avot de Rabbi Natan 12 claim that Aaron's having been a lover of peace was the reason why he was mourned even more than Moses when he died.