Jewish Fasting Laws and Guidelines

Estimated reading time: 13 minutes

Jewish law is called halachah, from the Hebrew word holech, to walk. The laws of the Torah shine their light upon every part of our lives[1], creating a clear path to walk through[2]. As we strive to fulfill these laws, we ourselves grow. We walk, or journey, to a higher place than where we began[3].

We pray for the day when everyone will follow the ways of the Torah, as the prophet Yeshaya foretold, “and the nations will walk to your light[4].”

This guide explains the Jewish fasting laws (halachot) of the Four Fasts, along with the lessons they teach. It answers common questions about Jewish fasting rules while presenting the halachah behind them.

The following ideas are gathered from various Torah sources, including Rabbi Shmuel Kamenetsky shilt”a in Kovetz Halachot.  The “lessons” are written in italics, to differentiate them from the “laws”. In truth, the Torah’s laws and its lessons are one and the same, as they both reveal what Hashem wants from us most. The following ideas are just a drop in the sea compared to all of the Torah of the Four Fasts, but, as Rabbi Tarfon teaches, “The task is not upon you to complete, yet you are not free to withdraw from it[5]“!

These laws are based on my best understanding of the halachah. Please note that we have followed Ashkenazic customs. If any questions arise, please consult with a qualified rabbi.

Table of contents

The Four Fasts

  1. The 9th of the Jewish month of Av, the 17th of Tammuz, the 3rd of Tishrei, and the 10th of Tevet are all fast days[6].
  2. These fasts, which were established by the Prophets, are known as “The Four Fasts”[7].
  3. By using them as opportunities for personal growth and improvement, the painful moments themselves will bring about the ultimate salvation. When Mashiach (the Messiah) comes, these fast days will all be annulled and transformed into Festivals, days of joy and happiness[8].

Self-Introspection

  1. The purpose of these fasts is to awaken our hearts to repentance. Therefore, one must contemplate his actions and search for ways to better them[9].
  2. It is a mitzvah (Torah commandment) to eat properly, to be healthy to serve Hashem. However, getting carried away with the physical world can prevent us from stopping to think what life is really about. On fast days we do not eat. We are like angels. Our time and minds are free to think about and remind ourselves what is truly most important in life[10].

Who Must Fast?

  1. All must fast on these fast days, including women[11].

Life-Threatening Situations

  1. In any situation of life-threatening danger, on may, and must, transgress any Torah prohibition to save his life[12].  If fasting will put one’s life at even the slightest risk, they must eat on the fast day.
  2. One must save himself or another in danger immediately, without asking a rabbi first; while stopping to ask, the sick person may get even weaker[13].
  3. The Torah tells us to live through the mitzvot (pl Torah commandments)[14]. The entire purpose of all mitzvot is to uplift our lives, filling them with happiness, well-being, and closeness to God. That is why the mitzvot themselves can be temporarily suspended in order to prolong one’s life, so he can fill it with even more happiness and mitzvot[15].

Expectant and Nursing Women

  1. An expectant woman is often exempt from fasting because she is often a little bit weak (see endnote[16]).
  2. Only if she is certain that she is strong enough to fast, must she fast[17].
  3. Similarly, a nursing woman is often exempt from fasting because she is often a little bit weak[18].
  4. Only if she is certain that she is strong enough to fast, must she fast[19].
  5. Even if she is not weak, but is concerned that fasting will cause her to run out of milk for nursing, she should not fast[20].

Eating a Little Bit at a Time

  1. If a nursing or expectant woman does not presently feel any pain or weakness, but is concerned that fasting may cause her to feel weak, she may eat and drink a little bit at a time[21], as follows:
    • a. After eating 32 grams[22] (just over an ounce) of food, she should wait nine minutes before eating again. She should do this every time she feels the need to eat[23].
    • b. If she cannot wait this long, she can eat within nine minutes. Nonetheless, she should at the very least try to wait two minutes before eating again[24].
    • c. Regarding drinking: if possible, she should wait between every cheek-full she drinks, as described earlier with regard to eating (steps a-b). However, if she cannot wait, she should drink less than one cheek-full at a time, wait a couple of seconds, and then drink less than a cheek-full again, and so on[25].
    • d. Although the cheek-full measurement depends on each individual, it is 40-45 grams (1.14-1.59 fluid ounces) for the average adult. Using a one-ounce shot glass will ensure that she does not drink more than this amount[26]. She can also use such a glass to measure her food[27], compressing the food to remove air spaces[28].
    • e. She need only wait between two foods or two drinks, not between a food and a drink[29].
  2. If she begins to feel significantly weak, she is immediately exempt from fasting. She may eat as usual without waiting or measuring her food[30].

A Sick Person

  1. Anyone who will feel significantly weaker by fasting than an average person who fasts, is considered to be sick (a choleh), and is exempt from fasting[31].
  2. A completely healthy person who knows that fasting will definitely cause him to get sick may eat a little bit at a time to prevent sickness, as described earlier (in the previous section)[32].
  3. Those who are completely exempt from fasting may eat as usual. They do not gain anything by eating a little bit at a time, or less than they usually do. They may eat immediately, and do not need to wait until they feel weak [33].
  4. Nonetheless, they should not indulge themselves by eating delicacies[34].
  5. If one would like to swallow a capsule to relieve a slight pain or weakness in his body, and cannot do so without drinking some water, s/he can drink a little bit of water[35] in order to swallow the pill. This is even if his particular sickness does not exempt him from fasting[36].
  6. The Talmud tells us that precisely when someone is ill and suffering, the Divine Presence rests above his head[37]. Similarly, precisely when things seem most bleak and hopeless, Hashem is close by and with us more than ever[38].

Children

  1. One may feed boys under 13 and girls under 12, as usual[39].
  2. Children who can understand what it means to mourn[40] should be trained to do so[41]. They should be told that it is a fast day, to take part in feeling with the mourning of the community, and to only eat simple foods in order to sustain themselves[42].

Various Dos and Don’ts

  1. One may not eat or drink even the smallest amount on a fast day[43].
  2. With the exception of the 9th of Av (Tishah B’Av), one may bathe himself, anoint or rub himself with oil or other substances for pleasure, wear leather shoes, and engage in marital relations on these fast days[44].
  3. However, one should ideally refrain from washing himself with hot water, even during the evening proceeding the fast[45].
  4. One may not wash his mouth with water or mouth wash on a fast day.[46]
  5. However, if not washing his mouth will cause him extreme discomfort (mitzta’er), he may wash his mouth. He should tip his head downwards while washing his mouth, to prevent the water from entering his throat[47].

An Accidental Blessing

  1. If one accidentally recited a blessing on some food or drink, and immediately afterwards realized that it is a fast day, he should taste a small amount of the food or drink, so that his blessing should not be in vain (a bracha levatalah)[48].

Eating before Daybreak

  1. One may eat before daybreak (alot hashachar) the day of the fast.
  2. However, before going to sleep the night before the fast, he should stipulate that he will eat the next morning before daybreak[49].
  3. If when going to sleep, one planned on getting up and eating before daybreak, but for whatever reason did not to stipulate, he may still eat in the morning before daybreak[50].
  4. One may not begin eating more than a k‘beitzah (“like [the size of] an egg”) of any bread-like food items (pat haba’ah b’kisnin; bread, cake, pastries etc.) within a half hour before daybreak. One who wants to eat such food before daybreak of the fast must begin eating before the half hour before daybreak[51].
  5. Someone eating before daybreak of the fast should not eat sweet foods. Their sweet taste may remain in his mouth during the fast, and will be swallowed when he swallows his saliva[52].

The Special Aneinu Prayer

  1. An individual who is fasting should recite the special Aneinu (“Answer us…”) prayer for fast days, in the blessing Shomei’a Tefillah (“Who answers prayer”) in Shemoneh Esrei (the silent Amidah prayer of eighteen[53] blessings)[54].
  2. An individual who is not fasting because he is exempt should not recite the Aneinu prayer[55].
  3. However, one who is obligated to fast, but mistakenly ate something, should recite Aneinu[56].
  4. Fasts days are an opportunity to cry to Hashem out of pain, both on a personal and communal level. Angels generally carry our prayers to Hashem. However, when we cry or pray out of pain with sincere concentration, our prayers bypass the angels, going directly to Hashem. Even if the angels would “close the windows” of the heavens to stop our prayers from being heard, Hashem will “create a hole” in the heavens, accept our prayers, and have mercy on us[57].

The 17th of Tammuz

  1. On the 17th of Tammuz, or Shiva Asar B’Tammuz, we recall five major tragedies that occurred to our ancestors:
    • When Moshe saw the Jews worshipping the golden calf, he broke the first tablets with the Ten Commandants engraved upon them.
    • The walls of Jerusalem were breached by her enemies.
    • The lamb-sacrifice (korban tamid), until then offered daily in the Holy Temple (Beit Hamikdash), was stopped.
    • The evil Apostomus (a Greek governor[58]) burned a holy Torah scroll.
    • An idol was placed in the inner chamber (Heichal) of the Holy Temple[59].
  2. Each letter in the Hebrew alphabet corresponds to a specific number. The numerical value of the Hebrew word tov, “good” is 17. Despite the greatest of tragedies, we still have the greatest thing possible, a personal connection to Hashem! Ultimately the 17th of Tammuz will become a festival, or Yom Tov (“Good Day”)[60].
Turn the inspiration of these fast days into lasting growth. Learn with a TorahMate and keep moving forward all year long.

[1] See Ohr Hachaim Hakadosh Vayikra, 26:3, 4th explanation

[2] See ibid., 24th explanation

[3] See Maharal, Gur Aryeh Vayikra, 26:3

[4] Yeshaya 60:3. The Malbim there explains that this refers to the light of the Torah.

[5] Pirkei Avot, end of chapter 2

[6] Zechariah 20:9; Kovetz Halachot pg. 11

[7] Yom Kippur is a Biblical obligation, and Ta’anit Esther (the Fast of Esther) was not instituted by the Prophets, rather accepted by the Jews upon themselves (Even Ezra, Zechariah 20:9; Rabbi Refael Presby shlit”a). These two fast days are not included in the Four Fasts; their laws may differ from the laws described here.

[8] Rambam, Hilchot Ta’aniot 5:19

[9] Mishnah Berurah 549:1

[10] Dr. Don Rosenblum

[11] Kovetz Halachot pg. 11

[12] Shulchan Aruch Y.D. 157:1; see also Shulchan Aruch O.C. 328:2; Rambam, Hilchot Yesodei HaTorah 5:1; Shemirat Shabbat K’hilchatah Vol. 1, Ch. 32. The sins of idol worship, adultery, and murder, are exceptions to this rule; one must give up his life to avoid committing them. There are other rare exceptions, as described in Shulchan Aruch Y.D. §157. Note that one must also transgress any Torah prohibition to care for any wound which can affect the body’s internal blood flow (makkah shel challal). This is because even if it does not seem to directly endanger to one’s life, such a wound can ultimately lead to a life-threatening infection (Rabbi Betzalel Rudinsky Shlit”a; Shulchan Aruch O.C. 328:3 with Mishnah Berurah §49).

[13] Shulchan Aruch O.C. 328:3 with Mishnah Berurah §6

[14] Vayikra 18:5

[15] Rabbi Shamshon Rafael Hirsch zt”l, commentary to Vayikra 18:5

[16] Kovetz Halachot pg. 12. Note that although expectant and nursing women are generally weak and exempt from fasting, there may be more room for stringency of the 9th of Av (Tishah B’Av), as opposed to the rest of the Four Fasts (Rabbi Dovid Apter shlit”a; see Shulchan Aruch O.C. 554:5; Rema O.C. 550:1).

[17] Pg. 12

[18]  Pg. 13

[19] Pg. 13

[20] Pg. 13

[21] Pg. 13

[22] It would seem that this measurement is subject to debate. Although some say that the amount one may not eat on a fast day is a kezayit (“like [the size of] an olive”), we have followed the opinions that it is the larger kakotevet (“like [the size of] a date”). See Kovetz Halachot pp. 24-25, footnote 2 for discussion.

[23] Rabbi Yehoshua Newirth zt”l, Shemirat Shabbat K’hilchatoh Vol. 1, Ch. 39. Note that he writes these guidelines with regard to Yom Kippur. Although there is more room for leniency with regard to other (non-Biblical) fasts, one should ideally (lechatchila) follow these same guidelines on other fast days as well (Rabbi Dovid Apter shlit”a).

[24] Shemirat Shabbat K’hilchatah Ch. 39

[25]Ch. 39

[26] Rabbi Eliyahu Wincleberg shlit”a. One can also measure this precisely, before the fast, by filling up one cheek with liquid and then spitting out the liquid into a cup. On the fast, they should drink slightly less than this amount in each sitting (Shemirat Shabbat K’hilchatah Vol. 1, Ch. 39).

[27] Rabbi Eliyahu Wincleberg shlit”a. See Shemirat Shabbat K’hilchatah Vol. 1, Ch. 39 for other methods of measuring this amount of food.

[28] Ch. 39

[29] Ch. 39

[30] Rabbi Dovid Apter shlit”a; Kovetz Halachot pg. 17

[31] Pg. 17. This is in contrast to the laws of Shabbat, where only one who is so weak that he needs to lie down is considered to be sick.

[32] Pg. 17

[33] Pg. 18

[34] Pg. 18

[35] He does not need to “ruin” the water by mixing in something with an unpleasant taste (pg. 31).

[36] Pg. 31

[37] Shabbat 12b; Netivot Shalom Vol. 2, pg. 223

[38] Tehillim 91:15

[39] Kovetz Halachot pg. 19

[40] See Rabbi Zev Smith shlit”a, What’s The Halachah? pg. 114, footnote 16: “The age at which children become obligated in mitzvot is approximately five or six years old and depends on the child’s intelligence and the particular mitzvah.” In our discussion of taking part in mourning on a fast day, this age is generally not below eight years (Kovetz Halachot pg. 20).

[41] Kovetz Halachot pg. 20. One may actually give them all of their meals as usual, even though this is more than their bare needs for sustenance. The main form of education (chinuch) here is fulfilled by verbally encouraging them to eat simple foods because of the fast (ibid. footnote 15).

[42] Pg. 20. However, one does not “lose” his fast unless he eats a kezayit (“like [the size of] an olive”; see however, note 22 of this article) or drinks a cheek-full (melo lugmav; Kovetz Halachot pg. 24-25).

[43] Pg. 24

[44] Pg. 26

[45] Pg. 26-27. Washing with lukewarm water is permitted (Rabbi Dovid Apter shlit”a).

[46] Pg. 33

[47] Pg. 33

[48] Pg. 29

[49] Pg. 34. If he did not stipulate, his going to sleep is considered to be a voluntary commitment to begin the fast, and he may not eat afterwards.

[50] Pg. 34

[51] Pg. 37

[52] Pg. 39

[53] The Shemoneh Esrei prayer actually includes nineteen blessings. The name Shemoneh Esrei means eighteen, because it originally consisted of eighteen blessings. Although an additional blessing was added later, the prayer retained its original name.

[54] Pg. 41

[55] Pg. 41

[56] Pg. 41

[57] Ra’avad, Tamim Dai’im 184, quoted by Rabbi Shimshon Pincus zt”l, Shearim B’tefillah, pp. 34-35

[58] Tiferet Yisrael, Ta’anit 4:6

[59] Mishnah Ta’anit 4:6

[60] B’nei Yissaschar Vol. 1, Months of Tammuz and Av, 2:1

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