Note: The following pertains to the four minor fast days, the Fast of Gedaliah (3 Tishrei), 10 Tevet, Fast of Esther (13 Adar) and 17 Tammuz. The fasts of 9 Av and Yom Kippur are stricter and have additional laws as well.

Why Do We Fast?

It is a mitzvah, ordained by the prophets, to fast on those days on which tragic events occurred to our forefathers. The purpose of these fasts is to stir our hearts to reflect on the ways of repentance, and to serve as a reminder of our own evil deeds and the deeds of our forefathers. By remembering these events, we will improve our ways, as it is written, “They will then confess their sins and the sins of their fathers.”1 2

Who Is Obligated?

Both men and women over bar and bat mitzvah are obligated to fast.

Pregnant and nursing women are exempt from fasting (many are strict and only refrain from fasting if it causes them discomfort).3

One who is sick, even if not in danger, is exempt from fasting.4

In many situations, an elderly or weak person may also be exempt from fasting, and should consult a rabbi.

One who is permitted to eat on a fast day, but whose exemption isn’t readily apparent, should try not to eat in public.5

Children below bar and bat mitzvah don’t fast.6 A child who is old enough to understand the concept of mourning should preferably be told to refrain from sweets (one need not, however, stop him from eating sweets if he is in the middle of doing so).7

One who accidentally eats after the fast has already begun should nevertheless continue fasting.8

When Does the Fast Start?

The four minor fasts begin at alot hashachar, dawn.9 If one wishes to go to sleep and wake up before dawn to eat, he should stipulate (at least mentally) before going to sleep that he isn’t accepting the fast until dawn. 10

See what time alot hashachar/dawn is in your locale.

Can I Rinse My Mouth and Brush My Teeth?

In general, one should refrain from rinsing his mouth or brushing his teeth on a fast day.11 If not doing so will cause one significant pain and discomfort, he may do so provided that he doesn’t swallow.12 (This leniency only applies to the minor fasts.)

How Do I Take Medication?

If necessary, one is permitted to take medicine, as long as it is unpleasant tasting.13 Preferably, it should be taken without water, but if that’s not possible, then he should put something bitter, such as vinegar, in a drop of water to help down the pill. If this can’t be done, and he will become ill if he does not take the medication, then the medicine may be taken with regular water.14

Vitamins and supplements, even if taken regularly, are not necessarily considered medicine for this purpose. If necessary, a rabbi should be consulted.

As noted, these guidelines apply to the minor fasts. A rabbi should be consulted with regard to the fast of 9 Av and Yom Kippur.

Can I Bathe, Shower or Swim?

One is permitted to shower, swim or bathe on a minor fast day.15 (There are those who have a custom to be strict and refrain from doing so with hot water.16)

May I Listen to Music?

Many are strict not to listen to music on a fast day.17 (Among those who are strict, some are lenient on the Fast of Esther, as it isn’t a day of mourning.18) On 17 Tammuz, one may in any event not listen to music, as it is the first day of the Three Weeks of mourning that culminate on the fast of 9 Av.

How Are the Prayers Different?

On a fast day, we add Selichot (penitential prayers) to the morning service and the long version of Avinu Malkeinu to both the morning and afternoon services.

Additionally, during the Amidah, the custom is to add the prayer of Aneinu. The Sephardic custom is to recite Aneinu during both Shacharit and Minchah. The Ashkenazic custom is for the congregation to only recite it during Minchah, and the chazzan recites it during the Repetition of the Amidah in both the morning and afternoon services as its own blessing between the blessings of Re’eh and Refa’einu (this is the Chabad custom as well).

One who is not fasting (e.g., for medical reasons) does not recite the Aneinu prayer.

Reading of the Torah

On public fast days, the verses in Exodus 32:11-14 and 34:1-10 are read both during the Shacharit and Minchah prayers. These verses discuss the aftermath of the Golden Calf incident, how Moses successfully interceded on the Israelites’ behalf and attained forgiveness for their sin. The Ashkenazic custom is that after the afternoon Torah reading, the special fast-day haftarah, Isaiah 55:6–56:8, is read.

Someone who isn’t fasting, for whatever reason, should not be called up to the Torah.19 (If one was called up to the Torah, then if it is Shacharit on Monday or Thursday he can go up. If, however, it is Minchah, or Shacharit of a different day of the week, then he should only go up if not doing so would cause him great embarrassment.20)

Charity

It is customary to give extra charity on a fast day.21 Some have the custom to give the equivalent of a meal to charity.22

When Does the Fast End?

The fast ends by tzeit hakochavim, nightfall. See halachic times for your locale.

Note: The custom is that on the Fast of Esther, one waits to break his fast until after the reading of the megillah by night. Additionally, when the fast of 10 Tevet falls on Friday, one breaks his fast after Friday-night kiddush.

May we merit the coming of the Messianic era, when as, our prophets tell us, “The fast of the fourth month, the fast of the fifth month, the fast of the seventh month, and the fast of the tenth month will be [days of] rejoicing and celebration and festivals for the House of Judah; and they will love truth and peace.”23