Esther 4:4, "And she sent clothing to clothe Mordechai, and to take his sackcloth off him, but he refused."
The Gemara says in Chullin 139b, Where do we find Haman in the Torah? "Did you eat from the tree I commanded you not to eat from?" (Bereishis 3:11) Where do we find Esther in the Torah? "And I will surely hide My face on that day." (Devarim 31:18) Where do we find Mordechai in the Torah? "Flowing myrrh" (Shemos 30:23), which the Targum renders as "meira dachya".
This passage is so strange that it seems like it should be found in the Midrash Pliah (a collection of incomprehensible Midrashim), not the Gemara! What do these verses have to do with Haman, Esther and Mordechai, other than the similarity in sound?
The Gemara says in Megillah 12a: Rabbi Shimon bar Yochai's students asked him, "Why did the Jews of that generation deserve destruction?" He said to them, "You tell me." They said, "Because they had pleasure from the meal of that wicked man [King Achashverosh]." He said to them, "If so, only the Jews in Shushan deserved to be killed, not those in the entire world." They said to him, "So you tell us why." He said to them, "Because they bowed to Nebuchadnezzar's image." They said to him, "So why were they saved?" He said to them, "They bowed only for show, so G-d only threatened them for show."
This is odd: nowhere else do we find that students asked their teacher a question and he replied, "You tell me."
The answer is that their question contained the assumption that the Jews really deserved destruction, and it was only their prayer that averted the catastrophe. Rabbi Shimon bar Yochai did not agree with that assumption - as we see, he held that G-d only threatened them for show. Never did He entertain the idea of destroying them. Therefore Rabbi Shimon bar Yochai answered the students, "You are the ones making this assumption, so you tell me why."
When Mordechai first heard about Haman's decree, he went out in the street in sackcloth and ashes, and called upon all the Jews to pray. Esther sent him normal clothes to put on, but he refused. She then sent him a message asking what was going on. Is it possible that the queen herself had not heard of the decree against the Jews? Also, when Mordechai told her to go to the king and beg him for mercy, and Esther was afraid to go, Mordechai said, "If you are silent at this time, salvation will arise for the Jews from another place, but you and your father's house will perish." Why did Mordechai include in his threat the idea that salvation would come in any case?
The answer to all these questions is that Mordechai held like the students of Rabbi Shimon bar Yochai, that the Jews were in real danger. They had to fast and pray to annul the decree. Esther, on the other hand, held like Rabbi Shimon bar Yochai, that it was only for show and there was no real danger. That's why she wanted him to put on normal clothes and get up from the dust. Haman, who was serious about the decree, held like Mordechai, that the Jews deserved it for eating from the king's feast.
That is the meaning of the Gemara in Chullin: the allusion to Haman in the Torah is, "Did you eat from the tree that I told you not to eat from?" In other words, the sin was that they ate something they shouldn't have eaten. The allusion to Esther is, "And I will surely hide My face on that day, because of all the evil that they did, for they turned to other gods." This is because, according to Esther, G-d hid His face temporarily and allowed the Jews to think that they were in danger, when in fact they weren't. This temporary scare was their punishment for "turning" to other gods - note that the Torah says "turned" and not "worshipped" since they did it only for show. And the allusion to Mordechai is "flowing myrrh", part of the incense recipe, because prayer is like incense (Tehillim 141:2), which annuls decrees (Bamidbar 17:11).
We find these same two opinions in the Midrash (Bereishis Rabbah 76:1): The Jewish people would have deserved to be destroyed in the time of Haman [for being afraid of Haman's decree and not trusting in G-d], had they not found themselves a precedent in Jacob their forefather. They said, "If Jacob, who had a promise of protect from G-d, was afraid of his brother Esau, we who have no such promise are certainly allowed to be afraid." But the prophet Yishaya chided them, "You forgot Hashem your Maker, who spreads out the heaven and founds the earth..." Yishaya held like Rabbi Shimon that there was nothing to be afraid of, since Haman's decree was only for show, but the Jewish people held like the students.
May G-d save the Jewish people from all evil decrees and plans as He did in the time of Mordechai and Esther.