2) Public fasts which could theoretically be ordained by a Rabbinic ‘Beis Din’ (legislative body) for a community or an entire region, because of lack of rainfall, epidemic or the threat of military attack, or the like.
While this type of fast is mostly a thing of the past, we will merely highlight some of its most general halachos, by quoting from the Rambam. We quote selected paragraphs from Mishnah Torah: Hilchos Taanios, Moznaim Pub., Chapters 1, 2 and 4, translated by Rabbi Eliyahu Touger
1:4) From Rabbinic law comes the requirement to fast whenever a tragedy befalls the community, until mercy is granted from Heaven. During these days the people cry out in prayer, plead and sound the trumpets. On these fast days, we cry out in prayer, offer supplications and sound the trumpets only. In the Temple, we sound both the trumpets and the shofar. The shofar blasts should be shortened and the trumpet blasts extended, for the mitzvah of the day is with the trumpets. The trumpets are sounded together with the shofar only in the Temple, as can be inferred from Tehillim 98:6: “Sound trumpets and shofar blasts before the King, Hashem!”
1:17) Whenever there is a communal fast that was instituted for a distressing circumstance, the community’s court and its elders sit in the synagogue and review the conduct of the city’s inhabitants, from the time the morning prayers were concluded until noon. They remove the stumbling blocks that lead to sin. They give warnings, enquire, and investigate all those who pursue violence and sin, and encourage them to depart from these ways. Similarly, they investigate people who coerce others and humble them. They also occupy themselves with other similar matters.
This is what would happen from noon until evening: During the third quarter of the day, they would read the blessings and the curses in the Torah, as implied by Proverbs 3:11: “My son! Do not despise the instruction of Hashem, and do not reject His rebuke.” As the Haftarah, they would read a portion from the prophets appropriate to the distress for which they are fasting. During the fourth quarter of the day, the afternoon service is recited, supplications are made, the people cry out to G-d and confess according to their capability.
2:1) We should fast and sound the trumpets in the following situations of communal distress:
Because of the distress that the enemies of the Jews cause the Jews, because of the passage of an armed force, because of a plague, because of a wild animal on a rampage, because of various species of locusts, because of the black blight and the yellow blight, because of falling buildings, because of an epidemic, because of the loss of our source of sustenance, and because of a lack of rain.
2:2) A city afflicted by any of these difficulties should fast and sound the trumpets until the difficulty passes. The inhabitants of the surrounding area should fast, but they should not sound the trumpets. They should, however, ask for mercy on their brethren’s behalf. We do not cry out to Hashem or sound the trumpets on Shabbos… except in the case of distress over the loss of our source of sustenance. In this instance, we cry out to Hashem even on Shabbos, but we do not sound the trumpets for this reason on Shabbos.
4:1) On each and every day of the final seven fasts for lack of rain, we pray in the following manner. The ark is taken out to the street of the city, and all the people gather together, while dressed in sackcloth. Ashes are placed on the ark and on the Torah scroll to heighten the grief and humble the people’s hearts. One of the people should take some ashes and place them on the head of the Nasi and on the head of the chief justice, so that they will be ashamed and repent. The ashes are placed on the place where one puts on tefillin. Everyone else should take ashes and place them on his own head.
4:2) Afterwards, one of the wise elders of the community stands before them while they are sitting. If there is no wise elder, a man of wisdom should be chosen. If there is no man of wisdom, a man of stature should be chosen. He should speak words of rebuke to them, telling them: “Brethren, it is not sackcloth and fasting that will have an effect, but rather repentance and good deeds. This is evident from the story of Nineveh. It is not stated with regard to the people of Nineveh, “And G-d saw their sackcloth and fasting”, but rather, “And G-d saw their deeds.” (Yonah 3:10). Similarly, in the words of the prophetic tradition, it is written, “Rend your hearts, and not your garments.” (Yoel 2:13) He should continue in this vein according to his ability until they are humbled and turn to G-d in complete repentance.
4:3) After this person has completed his words of rebuke, the community stands up to pray. They should choose a person suitable to serve as a leader of prayer on such fast days. If the person who spoke the words of rebuke is suitable to lead the congregation on prayer, he should. If not, another person should be chosen.
4:5) The chazzan should begin and recite the Shemoneh Esrei in the usual fashion until the blessing ‘Ga’al Yisrael’ (“…the Redeemer of Israel”). He then recites ‘Zichronos’ and ‘Shofaros’ (verses recalling G-d’s remembrance of the Jewish people, and the unique influence of the shofar, also recited as part of the Musaf prayer for Rosh Hashanah.) that relate to the difficulty facing the people. He should also recite the Tehillim #120 (“I called to G-d in my distress and He answered me”), 121 (“I lift my eyes up to the mountains”), 130 (“Out of the depths, I called You, O G-d”) and 102 (“A prayer of the afflicted, when he becomes faint”)
4:7) He then begins to add six blessings; these are added one after the other. In each of them, he recites supplicatory prayers which include pleas for mercy and verses from the Prophets and Writings, with which he is familiar. He concludes each of these blessings with the concluding phrases mentioned below…
MBY 580:1-3 Certain dates on which fasting was encouraged
Ed: This short siman - which concludes the entire section of Hilchos Taaniyos (!) - lists several calendar dates which commemorate historical national calamities. These were never ordained as mandatory, as those related to the Destruction of the Temples. As their observance is seldom observed, if at all, we have chosen not to summarize these dates in a lesson. Anyone interested in an enlightening review of significant events in Jewish history is invited to learn this siman on his/her own.
Baruch Hashem, this concludes our treatment of Hilchos Taanis and indeed the entire Volume V of Mishnah Berura! Please stay tuned for some lessons on Hilchos Rosh Chodesh, which appear in Volume IV.