Our Gemara on Amud Beis tells us that In the heat of rabbinic dispute, Rabbi Yehoshua used disrespectful language to express what he thought was bewildering illogic in Shammai’s position. Later, he regretted this impertinence, and the Gemara tells us that, “Throughout his days his teeth darkened because of all his fasts that he undertook to atone for having spoken inappropriately of Beis Shammai.”

Is it permitted to take extreme measures of penitence to the point of damage to your health? The simple understanding of many teachings that we shall soon see, is no it is not proper behavior. The isolated situations in the Gemara where we find pious individuals who behaved in this manner could be understood as extra-legal acts of passion and devotion. In other words, “Don’t attempt this at home.” Certainly in our times, extreme penitence has fallen out of favor in actual practice. 

However, poskim throughout history have taken varied approaches to this subject. Let us explore some of the notable opinions on this.

The classic teaching comes from the Gemara in a number of places, with statements from Rabbi Elazar Hakappar and Shmuel (Ta’anis 11a):

⁦Shmuel said: Whoever sits in observance of a fast is called a sinner, as it is inappropriate to take unnecessary suffering upon oneself. The Gemara comments: Shmuel holds in accordance with the opinion of the following tanna, as it is taught in a baraita: Rabbi Elazar HaKappar the Great says: What is the meaning when the verse states, with regard to a nazirite: “And he will atone for him for that he sinned by the soul [nefesh]” (Numbers 6:11). But with what soul did this nazirite sin? Rather, the nazirite sinned by the distress he caused himself when he abstained from wine, in accordance with the terms of his vow. ⁦And are these matters not inferred a fortiori? And if this nazirite, who distressed himself by abstaining only from wine, is nevertheless called a sinner and requires atonement, then with regard to one who distresses himself by abstaining from each and every matter of food and drink when he fasts, all the more so should he be considered a sinner.

The Rambam codifies this in Hilchos Deos (3:1):

The sages prohibited one from punishing himself with fast days. Concerning such and like matters Solomon admonished saying: "Be not righteous overmuch; neither show thyself wise; why wouldst thou destroy thyself" (Ecc. 7.16).

The Shalah objects to this approach, and states:

Those who say that the whole point of doing Teshuvah is to merely obtain forgiveness for one's sins, and to no longer go in his old path are mistaken. One must not approach repentance from that aspect, but one must repair the sins committed with each specific organ. Only when one does so will repentance "tear up all evil decrees in the world." (It seems that the Shalah holds the function of fasting and other afflictions is to expunge the effect of the sin from various parts of the body that benefited from and participated in the sin.)

Many people who read this statement by Rabbi Eliezer Hakappor use it as an excuse to indulge in wine, quoting the great scholar Rabbi Eliezer in support of their lifestyle. As a result, they are liable to die in a state still soiled by sin.

We will return to the Shalah shortly but first we must learn a Tosafos. Tosafos in Ta’anis raises a contradiction from another teaching also in the name of Shmuel (Bava Kama 91b), where Shmuel says though it is forbidden to directly injure oneself and therefore an oath will not be binding as the action is already forbidden, one indeed may take a oath in order to fast. This is based on a scripturally derived principle that all oaths must consist of a voluntary choice, and that to do or not do is permitted prior to the oath. Thus, if it is forbidden to injure oneself then no oath made with this intent is valid. However since Shmuel says one may make an oath to fast, this implies that it is not forbidden which contradicts his statement in Ta’anis.

Tosafos offers a fascinating answer with interesting moral and theological implications. True, it is technically a sin to cause oneself suffering. However, the zechus of causing the suffering for the purpose of atonement is greater than the sin, and thus it is permitted. Tosafos draws an analogy to fasting on shabbos to avert a dream with catastrophic portents. One is normally forbidden to fast on Shabbos, but if one had a troubling dream, he may fast on Shabbos to reverse or mitigate its effects. Yet, he also must fast AN ADDITIONAL FAST after shabbos to atone for the fast he made on shabbos (Berachos 31b). Amazing! So it can be a sin, but relatively more if a zechus than a sin and therefore permitted.

The shalah quotes Tosafos but argues for a simpler but also more stringent answer. Shalah holds that Shmuel not only permits but considers it an obligation to engage in numerous fasts. He quotes our Gemara (Chaggigah 22b), proving that one must do whatever it takes to purge the sin. That is what Shmuel means to say in Bava Kama. Even though Shmuel says it is permitted to fast, he really means obligated. The word “permitted” is used only in relative contradistinction to the other case he was discussing, which was self injury - and that is forbidden. In Ta’anis, where Shmuel forbids fasts, the situation is regarding someone who is not in need of repentance. Also Rabbi Elazar Hakappar calls the Nazir a sinner only if he adds days that are beyond what was necessary for self purification. However, the actual act of vowing to be a Nazir to purify yourself is a Mitzvah.

While the Shalah is an extreme position and it is unlikely that such behavior is recommended, there was a much more accepted idea, called Teshuvas Hamishkal. Literally it means weighed repentance and the idea is to induce suffering that is equal to the pleasure experienced from the sin (See Orchos Tzaddikim 26). You might also remember it from Tefila Zakah that is said Yom Kippur eve, where we acknowledge that really we should do Teshuvas Hamishkal, but we ask that our Yom Kippur be accepted in place of that. The Kol Bo (66) provides an extensive list of sins, and the process and number of fasts required for each kind of sin , as well as the Rokeach. It also is discussed amongst the poskim whether these fasts can be exchanged by giving Tzedaka. There is a formula provided in Shulkhan Arukh (OC 334:26, see Ramah), and it’s not cheap! The amount is based on the approximate cost of a sacrificial animal (see Mishna Berura 334:80). 

I don’t believe that it is a good idea to focus too much on these matters because most people are not strong enough to bear this kind of burden and it is likely to discourage penitence. There is precedence in Jewish thought that the rabbis lessened the strict requirements if they believed that ultimately it would sabotage and discourage repentance. For example, we have Takanas Hashavin (Gittin 55b). According to the Strict law,  If one stole a center beam and used it in his home, he would have to demolish the Home by removing the central beam and returning it to the rightful owner. However, the rabbis enacted an extra legal leniency, allowing him to pay for it even if the owner wants the original item, so he not have to destroy his house and be discouraged from Penitence. So though it is important for intellectual honesty to understand that our ancestors held themselves to a higher standard of penitence, this should inspire and humble us, not lead us to despair.