R’ Meir Arama explains the “many” to include the more prominent, less conformed Jews together with the poorer, more conformed Jews in the act of wearing sack and ash.
The Yerushalmi and Panim Acherim translate “rabim” (“many”) as meaning “the Rabbis.”
The Yosef Lekach writes that this is a reference to the reshus harabbim, the public thoroughfare. Perhaps he means to suggest that this phrase implies the participation of the general masses of Jews, like those who travel the public road. Otherwise, this may be a reference to the last stage of the five-step repentance program described in the Mishnah (Taanis 2:1), in which the aron — the synagogue Ark — is taken out into the public square, and ashes are placed on it and the community leaders.
The Jews responded to this news with a total of six actions: they mourned, fasted, cried, eulogized, and donned sack and ash. The M’nos HaLevi writes that there is significance to this number. These six actions correspond to the six days in which the Jews participated in Achashverosh’s party (see Esther 1:5). Indeed it was a seven-day party, and the Jews took a break from the last day because it was Shabbos.
Since the verse that describes Achashverosh’s party (1:4), the verse says the party lasted for many days (yamim rabim), and gives the number of days as 180, R’ Yehonason Eibshutz wonders why the phrase “yamim rabim” is not superfluous. He answers that this phrase refers to the kind of days they were, long summer days, concluding with Yom Kippur. This is the day on which no Jew sins. In fact, he adds that the gematria of the Satan (hasatan) is 364 (5+300+9+50), one less than the total amount of days in a solar year, indicating that the Evil Inclination has no hold on us for one days out of the year – Yom Kippur. Therefore, there were only six days for which the Jews needed to atone.
The Ginzei HaMelech writes that the Sfas Emes views Megillas Esther as the beginning of the Oral Law. Mordechai was even a member of the Anshei Kenesset HaGedolah (Men of the Great Assembly) that began the establishment of Rabbinic law. The Oral Law is represented by the number six, as that is the total number of Orders in the Mishnah – Seeds, Festivals, Women, Damages, Holy Items, Purity. The Jews mourned in six different ways in to show their new-found reverence for the Oral Law.
Interestingly, according to the Vilna Gaon, there are not six actions here, but five. In his understanding, the great mourning is not a separate action, but is one general action described with the remaining five detailed descriptions. According to him, these five correspond to the five actions Jews are supposed to take (Mishnah, Taanis 1:3-7) when they are suffering agriculturally.
On a simple level, Ibn Ezra tells us that this lowly dress would shame the monarchy.
According to the Me’am Loez, people were not allowed to wear sackcloth before the king because it was considered a bad omen as such people would thereby be walking reminders of death. For this reason, we find in the Torah (Bireishis 50:4) that when Yaakov passed away, Yosef was not allowed to have an audience with Pharoah.
Also, the Talmud (Brachos 62b) learns a kol v’chomer (a fortiori) argument that if in our verse, a person could not wear sackcloth (which, although is ugly, it is not repulsive) before a human king, how much more-so should one be forbidden from spitting (which is physically repulsive) in a synagogue, where one stands before the King of kings.
The Kabbalas Rabbah takes this idea one step further. If it is inappropriate to walk in front of a hum king looking like a mourner, how much more-so is it inappropriate to appear before the King of kings looking that way. In other words, in general, having a downcast negative attitude does not befit the servant of H-Shem. Even on the night of Rosh HaShanah, when we are judged, we are instructed to leave the synagogue confident in our positive judgment.
According to Rav Dovid Feinstein, Mordechai dressed in sack and ashes because the Talmud (Moed Katan 26a) writes that one should tear one’s clothing when one hears bad tidings.
Yosef Lekach adds that Mordechai’s sensitive emotions allowed him to feel the pain of the potential threat of genocide, that he mourned as if people had already died.
Seeing as nobody was allowed to enter the king’s gate dressed in such a manner (see Esther 4:2 below), the P’dus Yaakov writes that, by doing so, Mordechai was indicating that his rightful place was with the people rather than with the king.
In Pirkei d’Rebbe Eliezer, Mordechai is compared to the king of Ninveh (Yona 3:6), who is praised for immediately donning sack and ash upon hearing that H-Shem planned to destroy his city for their erstwhile evil behavior.
It is possible that, by using ash, Mordechai was invoking the merits of the Jewish forefathers. R’ Elazar of Germiza writes that Mordechai chose ash to recall before H-Shem the merit of our forefather, Avraham. After all, Avraham risked his life to prove the truth of monotheism by being thrown into a flaming furnace. In recognizing H-Shem’s Mercy in saving his life, he later called himself no more than “dust and ash” (Bereishis 18:27). According to the Targum, Mordechai was invoking the merit of another forefather, Yitzchak. Because he laid himself down on an altar dutifully prepared to be slaughtered like a sacrifice by his father (ibid. 22:9), H-Shem credits him with remaining as ash on the sacrificial altar. Finally, Mordechai invoked the merit of Yaakov, who wore sack after the sale of Yosef (ibid. 37:34). The Maharal notes that the verse in Tehillim (20:2) invokes “the G-d of Yaakov” in that fervent prayer for salvation because Yaakov was the forefather whose difficult life deserved more of H-Shem’s Mercy.
R’ Elazar Shach points out that the Midrash (Bereishis Rabbah 84:19) teaches that the Jews of Egypt wore sack before their miraculous redemption. By tapping into this ancient tradition, Mordechai was showing his faith in H-Shem and the Torah.
On a more mystical note, R’ Raphael Moshe Luria writes that Adam and Chava before the sin wore “ohr” (light, spelled aleph-vuv-reish), but were demoted to the status of needing to wear “ohr” (skin, spelled ayin-vuv-reish) as a result of the sin. Based on R’ Moshe Cordevero, Rav Luria continues with the idea that garments of light help one to serve H-Shem, and this is why one was not allowed to enter the “king’s” gate when not properly dressed. Doctors must shed their suits to don scrubs, rubber gloves, and bouffant caps for surgery. The soul, too, must shed the Divine light in which she is dressed to don the hazmat suit that is the earthly body to utilize the physical world in a continued effort to fulfill H-Shem’s Will. In our analogy, the difference between the soul and the doctor is that the soul’s skin automatically turns into light with the achieving of a spiritual goal.
The Ginzei HaMelech brings down from the AriZal that the gematria of “sak” (sack, 300+100=400) is an allusion to the four hundred officers whom Esav commands in his meeting with Yaakov (Bereishis 33:1). Kabbalistically, these themselves represent the four hundred powers of tuma, or manners in which impurity can enter our lives. He brings from the Imrei David that wearing sackcloth [perhaps through its ability to instill humility] gives one the ability to fend off impurity.