Halacha for Wednesday 5 Shevat 5777 February 1 2017

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 Thus, even when it seems that the reason behind these laws change or are no longer applicable, nevertheless, the law remains unchanged.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

The Laws of Precedence Regarding Blessings (Continued)

In the previous Halacha we have explained that there are instances that priority is given to recite a blessing upon a certain food over another because of the innate significance of the given food, for instance, because it is a fruit that belongs to the Seven Species of fruits that the Land of Israe......

Read Halacha

The Month of Shevat and the Law that Food Must be in Front of the Individual While Reciting a Blessing

Next Wednesday (actually, beginning from next Tuesday night) will mark the Fifteenth of Shevat or Tu Bishvat. We will therefore begin a segment on the laws of Blessings of Enjoyment. In following Halachot we shall discuss some more laws pertaining to reciting blessings which we have discussed in the......

Read Halacha

Precedence Regarding the Order of Blessings (Continued)

Summary of the Laws Explained Thus Far In the previous Halachot we have explained that there is an order of priority regarding blessings, sometimes because of the innate importance of the food and sometimes due to the importance of the blessing. Priority of “Boreh Peri Ha’etz”......

Read Halacha

The Laws of the Blessing on Fruits

In the previous Halachot we have explained that there is an order of priority regarding blessings. Thus, if one wishes to partake of apples and dates, one must recite the blessing on the dates, for they are one of the Seven Species. Precedence Regarding Blessing-Only Preferable Maran Ha’Be......

Read Halacha


Question: Is one permitted to act stringently in any situation one pleases?

Answer: In the previous Halacha we have discussed that one must wait six hours between eating meat and cheese in accordance with the ruling of Maran Ha’Shulchan Aruch. This law is based on a Gemara in Masechet Chullin (105a). For the purpose of our discussion, we shall quote the words of the G......

Read Halacha

Eating Meat Dishes after Dairy Foods

In the previous Halachot, we have discussed the laws of eating dairy foods after meat. We have explained that one must wait six hours between eating the respective foods. We shall now discuss the laws of eating meat dishes after dairy foods. The Opinion of the Gemara which Permits Eating Meat aft......

Read Halacha

Some Detailed Laws Regarding Eating Cheese after Meat

In the previous Halachot we have mentioned that after eating meat, one must wait six hours before eating dairy products. A Woman who has Given Birth or is Nursing A woman who is within thirty days of having given birth may eat dairy products after eating meat and she need not wait six hours. It ......

Read Halacha

Eating Dairy Items after Eating Poultry

In the previous Halacha we have discussed in general the law that one must wait six hours after eating meat before eating dairy foods either because the nature of meat is to get stuck between one’s teeth or because meat gives off a taste in one’s mouth for a prolonged amount of time. ......

Read Halacha