Tana d'Bei Eliyahu (ch.20) writes that when Agag, the king of Amalek, was captured (by Shaul HaMelech and his army), he cried and moaned in prison. He said, "Woe to me. Perhaps I will not leave descendants in the world!" Tana d'Bei Eliyahu says that in the merit of these tears, he merited descendants, and Haman came from him. Reb Chaim Kanievsky zt'l says that we see from this source the amazing power of tefillah. It doesn’t make a difference who is praying or what he is praying for. Tefillah is so powerful before Hashem that every prayer has an effect. Agag was a rasha, from the family of Amalek, and his prayers were that he should have offspring, which is entirely against Hashem's will. Hashem wants Amalek's memory to be erased – not perpetuated. Nevertheless, his tefillos were answered. That is the power of tefillah. Let us learn from this that when a Yid davens to Hashem, and his requests are the will of Hashem, the tefillos will be very effective.
After reading the megillah, we say שושנת יעקב, and we say, יכלמו ולא יבושו לא קויך שכל להודיע בך החוסים כל לנצח, "To make known that all those who trust in You, they will never be embarrassed – all those who trust in You." The Brisker Rav zt'l (ג"פ 'עמו ז"הגרי פניני) explains that this means that the purpose of Megillas Esther is to make known that Hakadosh Baruch Hu answers the tefillos of Bnei Yisrael when they call out to Him.
Taanis Esther is a day for tefillah. The Divrei Chaim zt'l would stay in his room throughout Taanis Esther. When a question arose, he would answer it quickly and return to his avodah. Also, Rebbe Levi Yitzchak of Berdichev zt'l would spend the entire day of Taanis Esther alone with his Creator. On Taanis Esther, no one was able to talk to him about matters of this world. Tzaddikim said that due to the Berdichever Rav's avodah on this day, he subjugated the kelipos of the seventy nations.
One year on Purim, Rebbe Shimon Nosson Nata zt'l, the Lelover Rebbe, was in his room for a very long time. Many people arrived to give him mishloach manos. They were waiting outside his room, but he wasn’t coming out, and he didn't open the door for them. Reb Matisyahu Deutsch z"l was there, and he filled his heart with courage and opened the Rebbe's door. He apologized to the Rebbe for disturbing him but explained that many people were waiting for him. The Lelover Rebbe replied, "My avodah of the entire year is dependent on Purim. Do you want to take this away from me?" Then he instructed him to leave the room and to close the door behind him.
His son, Reb Moshe Mordechai of Lelov zt'l, would do something similar. He spent a lot of time saying Tehillim on Purim. We should learn from their ways. Purim is an ideal time to invest in tefillah and to arouse Hashem's compassion for His children.
יוסף כצאן נוהג (printed in Frankfort, year 5478) writes that the custom is to come to the beis medresh a little earlier than usual on Purim morning, so one can finish Tehillim before Netz HaChamah, and then to daven Shacharis. One year, at the Purim tish of the Beis Avraham zt'l, he spoke about the importance of tefillah on this day. He discussed the pasuk (Esther 8:3) לוֹ וַת ִּתְח ַנֶּן וַת ֵּבְךְּ, "She wept and beseeched him." It states וַת ִּתְחַנֶּן, and not וַתִּחַנֶּן. This means that she and her entire essence became one with her tefillah. Her request was לוֹ, to be close to Hashem (Avodas Pnim).
The Gemara (Megillah 5a) says, של נטיעה נטע רבי בפורים שמחה, Rebbe planted a plant of joy on Purim. Generally, planting isn't a time for joy because one doesn't know whether the plant will grow or not. The joy is when one harvests the fruits, as it says (Tehillim 126:5) יִק ְ צֹרוּ בְּרִנָּה בְּדִמְעָה ה ַזֹּרְע ִים, "Those who tearfully sow will reap in glad song." However, on Purim, there is joy when one plants, because he is sure that it will grow well, and he will earn a good profit from his efforts. This is because the gates of heaven are opened wide on this day, for every person, and the wise draw from this day refuos and yeshuos with their tefillos.
There is a saying from generations ago regarding Purim, הדור צדיק א ווערט שמוגער יעדער, every simple, regular person becomes the tzaddik of his generation on Purim. Everyone receives the amazing power on Purim to annul decrees and to draw down yeshuos with his tefillos.
