Taanis Esther-A Yom Segula:
The Kav Hayashar writes that on Taanis Esther the gates of mercy are open, and it is hence an auspicious time for Hashem to accept one’s prayers. On this day one should recite psalm 22, which was recited in reference to Esther, and then supplicate to Hashem for whatever matter he needs salvation. He is to Daven that in the merit of Mordechai and Esther his prayers will be answered.
The reason behind the fast:
This fast commemorates the fast [of Esther] on the 13th of Adar, which was the day of battle with our enemies. The fast does not commemorate the three day fast that took place in Nissan. The Kabalistic reason behind the fast is in order to weaken the prosecution of the Satan who prosecutes against the Jewish people who eat and drink on Purim. Other Kabalists explain that the decree of Haman was never fully nullified but was rather switched for occasional suffering, thus we fast each year as atonement to nullify the remaining decree of Haman.
Summary of Taanis Esther
- The 13th of Adar is an accustomed fast day. When Purim falls on Sunday, the fast takes place the previous Thursday, the 11th of Adar.
- The fast begins at Alos Hashachar of the day of the 13th of Adar. This is approximately two fluctuating hours prior to sunrise. If one slept [even on the couch] and then woke up prior to Alos he may not eat, unless he stipulated prior to going to sleep that he plans to eat after awaking before Alos. He may however have a drink, even if he did not stipulate before going to sleep, although initially it is proper to stipulate before going to sleep even if one only plans to drink and not to eat.
- One who is sick or is experiencing a great amount of pain is exempt from fasting on Taanis Esther. Pregnant and nursing women are exempt from fasting on Taanis Esther. Children are not required to fast, even for a few hours. However they are not to be given sweets and the like, although one is not required to stop them from eating it if they are in the midst of doing so.
- The Maharil would not give a class on Taanis Esther in order so people are able to properly prepare for Purim.
- One does not rinse his mouth, brush his teeth, or use mouthwash, during a fast day, unless he feels extreme discomfort.
- Selichos is recited after Shemoneh Esrei of Shacharis. When reciting Selichos without a Minyan one omits the 13 attributes of mercy, and the parts in Aramaic.
- Avinu Malkeinu is recited after Selichos.
- The Chazan recites Aneinu in his repetition of Shacharis. It is not recited by anyone in the silent Shemoneh Esrei of Shacharis. At Mincha everyone says Aneinu in Shemoneh Esrei.
- Prior to Mincha one is to give Igara Ditaanisa to charity. [The fast “tax” which consists of the money worth of meals saved by fasting. This money is given to charity.]
- The Torah is read by Mincha with a Haftorah and is returned to the ark after Yehalelu, prior to the half Kaddish.
- Birchas Kohanim is recited in the Chazan’s repetition of Mincha. In Jerusalem, Nesias Kapayim is performed if Mincha is taking place past Plag Hamincha.
- Tachanun and Avinu Malkeinu are omitted by Mincha, with exception to when Taanis Esther is pushed up to Thursday.
- It is forbidden to eat or drink after the fast until the conclusion of Megillah reading. In a time of great need one may eat a small snack and have a drink.
- The Half Shekel: The half Shekel donation is given on Erev Purim prior to Mincha. When Purim falls on Sunday, the half Shekel is given on Taanis Esther, which is on the previous Thursday. However in Jerusalem and other walled cities it is given on Sunday. One is to give three half coins to charity. Each coin is to be half of the currency amount used in one’s country. Hence in the Unites States that the currency is one dollar, one is to give three half dollar coins. In Israel that the currency is one Shekel, one is to give three half shekel coins. [Some Poskim however rule that if one has the ability, he is to give a half coin which contains real silver and is worth at least the monetary value of the half Shekel in the times of the Temple. As of January 2015 one gram of silver was worth $.57 for a total of $5.47 for the half silver Shekel.] The custom is for the father of the house to give three half coins on behalf of each member of his family, including his wife and small children [both male and female], and including even for the fetus of a pregnancy. It is best to give the children money for them to fulfill the Mitzvah themselves. One may donate the money to a Shul or for other Mitzvah purposes.
- Mincha of Erev Purim that falls on Shabbos: If Erev Purim falls on Shabbos, Tzidkascha Tzedek is omitted from Mincha of Shabbos.
 Chapter 97
 Psalm 22 refers to Esther which said “Keili Keili Lama Azavtani”. It is also from a verse in this psalm [“Ekra Yomam Velo Seaneh Valayla Velo Dumiya Li”] that the obligation to read the Megillah at both night and day is derived from. [Kol Bo 45; Shulchan Gavoa 693/2; Kaf Hachaim 693/4]
 Midrash Tanchuma Bireishis; Abudarham [in Seder Tefilos Hatanios]; Levush; M”B 686/2; Kitzur SHU”A 141/2
 See next footnote
 On the 13th of Adar the Jews had to fight for their lives against the enemies. On a day of battle it is customary to fast to arouse Divine mercy and supplicate to Hashem to help them win the battle. This is seen from the fact that in the first battle with Amaleik that took place in the times of Moshe, Moshe fasted. Thus in commemoration of this fast we are accustomed to fast every year on the 13th of Adar. [Levush; M”B 686/2; Kitzur SHU”A 141/2] The Midrash Tanchuma ibid states that the Jews gathered on the 13th to wage battle and on that day they decreed a fast. In Likkutei Sichos 6 p. 371 the Rebbe explains that only Esther fasted on that day as she was the only one not in danger. However all the other Jews were threatened by the enemies and hence needed to eat in order to have strength for battle. It is for this reason that the fast is called Taanis Esther, as only Esther fasted.
 The Abudarham explains [in Seder Tefilos Hatanios] that the fast of Esther cannot be due to the three day fast which the Jews fasted on her behalf being that a) that fast occurred in Nissan and not in Adar, and b) we do not fast three days. Thus he concludes that the fast is rather due to that the 13th was a day of gathering [of which the Levush explains that it was a day of war which was a customary fast].
 Maggid Meisharim Vayakhel brought in Kaf Hachaim 686/8
 See Sheivet Hakehasi 1/203