The Me’am Loez writes that they decided on the name of the holiday being Purim because the lots being rolled in Nissan, and coming up with the date in Adar eleven months later gave the Jews time to pray and to repent.
Furthermore, Adar had previously had no other holidays, so Purim’s falling out then made it stand out more conspicuously as a holiday, receiving the attention it deserves.
Also, the Vilna Gaon and Malbim point out that the lots pointed to a potentially bad fortune, but H-Shem reversed it to a good fortune.
In quoting Rabbeinu Yona’s Shaarei Teshuva (2:4), the Ginzei HaMelech notes that just as sin can be transformed to a mitzva status if the sin leads to teshuva (“repentance”), so too the lots lead directly to the Jews’ redemption.
The Ksav Sofer supports this point by writing that in calling the day Purim, we celebrate the pain suffered by the Jews at this time, since it led directly to their re-acceptance of Torah (Esther 9:27).
Rav Moshe Feinstein wrote that the message to be learned from this is that one should never overconfident of one’s “lot,” thinking that one’s greatness in Torah knowledge or observance will necessarily parry off the Evil Inclination. Rather, even such a person should be always mindful of one’s potential to fall prey to one’s natural, animalistic urges.
In explaining how ora (“light”) represents Torah, the Ben Ish Chai writes that ora is written with a hey because it means ohrhey, or the light of H-Shem.
Rav Tzaddok HaKohen writes that ora is written with a letter hey because the verse intends it to be feminine since the Torah being described here is specifically Torah she’bal peh (“the Oral Law”). As Rashi (on Mishlei 1:8) writes, the Torah she’bal peh is represented by the feminine. Rav Mordechai Gifter explains that this is because the rabbis know the natural foibles of their people in the same way that a mother considers the nature of her son.
From the time the Jews ignored Mordechai (the leading rabbi of the generation) by attending Achashverosh’s party until they re-accepted the Oral Torah with the words (Esther 9:27) “kimu v’kiblu” (“they took and they accepted”), the Jews of that period were struggling with Torah she’bal peh, and its necessary rabbinic accompaniments.
Similarly, the Midrash Yerushalmi interprets yikar as denoting the judges, who were also the rabbis.
Midrash Chaseros v’Yitaros writes that sasson (“joy”) is spelled incomplete (without a vuv) because no joy can be complete until Moshiach comes and the Beis Hamikdash is rebuilt, bimheira biyameinu.
R’ Chaim Kanievsky writes that it is written incompletely because circumcision, which this represents, has an element of pain. He notes that sasson is spelled completely in the next verse (Esther 8:17) because we should strive to add to the joy of Purim as though nothing is missing, as the Halacha (Biur Halacha 695, dh “ad d’lo yada”) states explicitly regarding the custom to become inebriated on Purim.