What is the significance of the third day?
Torah Temimah citing Esther Rabah: Yisrael are not put in affliction for more than three days 1 . Also Yosef incarcerated his brothers for three days (Bereishis 42:17-18), Yonah was in the fish for three days (Yonah 2:1), and in the future, "ba'Yom ha'Shelishi Yekimenu v'Nichyeh" (Hoshe'a 6:2).
Why didn't the Midrash say that on the third day, she had the merit of the Jews of Shushan fasting for three days? Perhaps it asks why she didn't wait until they finished fasting the full three days. Or, it asks why she called the fast for three days. The Bavli (Yevamos 121b) holds that they fasted 72 consecutive hours; more than this would be too dangerous. However, the Midrash disagrees (refer to 4:16:4:2 and the note there). She could have decreed more, whether they ate at night (Anshei Ma'amad fast four consecutive days during the day - Ta'anis 27b), or if they were non-consecutive full-day fasts! (PF)
Why does it say "va'Tilbash Esther Malchus"? It should say 'Bigdei Malchus'!
Rashi citing Megilah 15a: Rather, Ru'ach ha'Kodesh clothed her 1 . It says here "va'Tilbash", like it says "v'Ru'ach Lavshah Es Amasai" (Divrei ha'Yamim I, 12:19). This teaches that Esther was a Navi.
Rashi: It means Bigdei Malchus.
Malbim: Kingship clothes her, and it was her size. All who saw her recognized that kingship is proper for her. This is like "Tzedek Lavashti va'Yilbasheni" (Iyov 29:14).
Vilna Gaon, from the Zohar: Ru'ach ha'Kodesh clothes only a broken body, therefore she received it only now [on the third day of fasting. Yitzchak blessed Yakov with Ru'ach ha'Kodesh after eating; perhaps his body was considered broken, from the root he was blind. - PF]
What is the significance that he was "Yoshev Al Kisei Malchuso b'Veis ha'Malchus Nochach Pesach ha'Bayis"?
Vilna Gaon: This was Hashgachah, so he will see her immediately. The throne is in place of Mishpat. He was not in the special room where he always is, and he was facing the opening.
Malbim: Beis ha'Malchus was close to the Chatzer. There he sits on his throne to judge the nation. Beis ha'Melech was inside. He was always in Beis ha'Melech when he was not engaged in needs of conducting the nation. Esther stood opposite Beis ha'Melech that is special for him. Via Hashgachah, now he was in Beis ha'Malchus near the Chatzer, and he set his throne facing the open, so he saw her immediately.
