Halacha for Monday 15 Cheshvan 5781 November 2 2020

Killing Lice on Shabbat

Question: May one kill lice on Shabbat?

Answer: One of the forbidden works on Shabbat is “taking a soul” (or killing), for instance, slaughtering an animal on Shabbat in order to eat it is a Torah prohibition.

The Gemara (Shabbat 107b) states that our Sages derive the prohibition of killing on Shabbat from the Mishkan (Tabernacle), for in the Mishkan, they needed to kill rams in order to dye their skins red and use them for different purposes in the Mishkan. Our Sages explained that only animals and living creatures which reproduce may not be killed on Shabbat; however, creatures which do not reproduce may be killed on Shabbat. Thus, our Sages said that it is permissible to kill lice sometimes found in one’s hair on Shabbat since such lice do not reproduce and are merely created from the sweat in one’s head. The Rambam (Chapter 11 of Hilchot Shabbat) and Maran Ha’Shulchan Aruch (Chapter 316) rule likewise.

Approximately two-hundred years ago, one of the great sages of Italy, Hagaon Harav Yitzchak Lampronti, discusses in his Sefer Pachad Yitzchak (topic of “Tzedah”) a new finding of scientists in his generation that lice reproduce through male and female like any other living creature and based on this discovery, it should be forbidden to kill them on Shabbat. He writes that he sent this question to his teacher, Rabbeinu Yehuda Bri’al, to which the latter responded that we do not have the authority to change any tradition we have received from our Sages, even when the opinions of scientists and researchers contradict them.

Indeed, Hagaon Harav Eliyahu Eliezer Dessler zt”l writes in his Sefer Michtav Me’Eliyahu (Volume 4) that all of the laws recorded in the Talmud were based on oral traditions our Sages received passed down from generation to generation, tow which they offer explanations of their own. Thus, even when it seems that the reason behind these laws change or are no longer applicable, nevertheless, the law remains unchanged. Hagaon Harav Yitzchak Eizik Ha’Levi Herzog zt”l writes likewise in his Responsa Heichal Yitzchak (Chapter 29).

In the past generation, some authors have arisen and claim that the Sages of the Talmud erred in their claim that lice do not reproduce, for it is well-known in our day and age without a shadow of a doubt that they do indeed reproduce and they do not generate spontaneously. These authors claim that all of our greatest Sages, including the Tanaim, Amoraim, Geonim, and Rishonim, were not aware of this reality.

We must analyze this fact, for every woman knows that sometimes there are lice and/or lice eggs (“nits”) in their children’s hair. It is clear that these lice reproduce. It is also clear that it is impossible to claim that our Sages did not realize this reality. Furthermore, they established a halachic verdict that only creatures that reproduce may not be killed on Shabbat but those that do not reproduce may. If we claim that all living creatures are products of reproduction, this would mean that there is no halachic ramification as it relates to this ruling of the Sages which they certainly obtained from an oral tradition!

Indeed, we already find a reference to lice eggs in Pirkei De’Rabbi Eliezer (Horeb edition, Chapter 26). Similarly, the Sefer Ohel Mo’ed, authored by one of the great Rishonim, explains that lice have eggs. We can likewise deduce from Rashi’s commentary on the Talmud (Avodah Zara 3b) that there is such a reality as lice eggs, as we are all aware of today. Nevertheless, they did not take the liberty of contradicting the opinion of our Sages because of this and they did not rule that killing lice on Shabbat is forbidden.

Indeed, even modern researchers admit that it is possible that lice multiply by laying eggs while not through conventional reproduction (male and female), as is the case regarding other living creatures. Regarding lice, the female is able to lay eggs on its own without male intervention. Such multiplying is not considered reproduction like rams, bulls, or other animals the Torah refers to in the context of the Mishkan and thus, it is permissible to kill lice on Shabbat even nowadays. (There are differences of opinion regarding this matter even among researchers themselves.)

Throughout the works of the great Rishonim, we find references to different types of insects and crawling creatures and the Poskim differentiate between those that reproduce conventionally and those that do not. They refer to these insects by their exact names in either Arabic or French; until today, these insects are still referred to by those exact names. We see clearly that the Rishonim were extremely well-versed in their knowledge of which creatures reproduced and which did not. Indeed, one of the earlier Rishonim, the Ra’avaya (Rabbeinu Eliezer ben Yoel Ha’Levi, one of the Tosafists) writes in his work (Volume 1, Masechet Shabbat, Chapter 136) that just as it is permissible to kill lice on Shabbat, it is likewise permissible to kill lice eggs on Shabbat; this does not constitute any prohibition of trapping or killing on Shabbat. Here too, clearly, the Ra’avaya was familiar with the reality of lice eggs and yet, this did not cause him to change the law.

Maran Rabbeinu Ovadia Yosef zt”l rules likewise in several of his works (including in his Chazon Ovadia-Shabbat, Volume 5, page 128) that in any event, we do not deviate from the words of the Sages of the Talmud, the Rishonim, and Maran Ha’Shulchan Aruch and it is permissible to kill lice even nowadays.

Ask the Rabbi


8 Halachot Most Popular

Megillah Reading- Coronavirus

Every member of the Jewish nation is obligated to read the Megillah on the day of Purim. One must read it during the night and once again the next day, as the verse states, “My G-d, I call out to you during the day and you do not answer; during the night I have no rest.” This verse is wr......

Read Halacha

The Laws of Hearing Parashat Zachor- Coronavirus

“Remember What Amalek Has Done to You” On the Shabbat preceding Purim, which is this coming Shabbat, after the opening of the Ark immediately following Shacharit prayers, two Sifrei Torah are removed; in the first one, we read the weekly Parasha (which is Parashat Vayikra this year, 577......

Read Halacha

Caution Regarding Chametz Issues

Our Sages (Tosefta Pesachim, Chapter 3) taught: “We inquire about and expound the laws of Pesach from thirty days before Pesach.” Based on this, great rabbis throughout the generations have taken the opportunity to teach the laws of Pesach to the public between Purim and Pesach since eve......

Read Halacha

The Laws of Koshering Vessels for Pesach

One may not use Chametz vessels on Pesach since vessels which have been used to cook in or have had hot Chametz placed in them have Chametz flavor absorbed in them. Thus, just as we separate between meat and dairy utensils all year long, we must likewise separate between the utensils we use all year......

Read Halacha


Matanot La’Evyonim- Coronavirus

In the previous Halacha we briefly discussed the Mitzvah of “Matanot La’Evyonim” on Purim day which is the distribution of two monetary gifts, one to each pauper. What Must One Give? In order to fulfill this Mitzvah, one need not give actual gifts; rather, it is permissible to ......

Read Halacha

Silver Vessels

Question: May one continue to use silver vessels or utensils, such as a Kiddush goblet, on Pesach after they have been used throughout the rest of the year? Answer: All vessels used all year round with cold foods or beverages may be used on Pesach after having been thoroughly washed beforehand, f......

Read Halacha

The Days of Purim and the Laws of Mishloach Manot- 5781

The Days of Purim Purim will be celebrated in approximately two weeks from today. This year, we must discuss several unique laws, first of all, because Purim day (the 14th of Adar) falls out on a Friday. Second of all, in Jerusalem, a “three-day Purim” will be celebrated since the 15th ......

Read Halacha

The Mitzvah of the Purim Feast This Year (5781)

Holding the Purim Feast at Night The holiday of Purim is different than all other holidays we celebrate in that whereas regarding other holidays the Mitzvah of partaking of a joyous holiday meal applies during the day and night, regarding the holiday of Purim, there is only a Mitzvah to hold a feas......

Read Halacha