141:1 When the month of Adar begins, we increase our joy. A Jew who has a legal matter pending with a non-Jew should have the case judged in this auspicious month.
141:2 In the days of Mordechai and Esther, the Jews gathered together on the thirteenth of Adar to defend themselves against their enemies. They needed to ask mercy from G-d to assist them. When the Jews went to war, they would fast so that G-d would aid them, as Moses did when we went to war against Amalek. Because of this, we can assume that at the time of Mordechai and Esther, they fasted on the thirteenth of Adar. This day has been accepted by the Jewish people as a communal fast called the Fast of Esther, a reminder that G-d watches us and hears each person’s prayers in his time of trouble when he fasts and sincerely returns to G-d, just as He did for our ancestors in those days.
This fast is not as stringent as the four fasts mentioned in Tanach, so one may be lenient in a case of need. Pregnant and nursing women and those who are ill – even if not dangerously so – need not fast if they will suffer great discomfort. Similarly, a woman who has given birth in the past thirty days and a groom during the seven days following his wedding need not fast. These people should make up the fast at a later date. Other healthy people, however, should not deviate from fasting with the rest of community. If one is on a journey so that fasting would be difficult, he is nevertheless required to fast.