Kiddushin 39 ~ Half Way There

For those studying the Daf-Yomi, one-page-a-day-cycle, tomorrow is an important day. A very important day. The present cycle of study began 1,355 days ago, on January 5th, 2020. And in another 1,355 days, on Monday June 7, 2027, the cycle will be completed.  And so Kiddushin 39 marks the halfway point, page 1,356. There are 1,355 pages completed, and another 1,355 to go. If you have been studying the last 1355 pages, (or even if you joined at some later time), now is a good opportunity to congratulate yourself, or your favorite daf-yomi teacher.

Are we there Yet? 

If you drove from New York to Los Angeles, it would take you about forty hours of driving to cover the 2,789 miles.  If you took Interstate 80, the halfway point on that journey would be at mile 1,395 which means a pit stop at the Wood River West State Wildlife Management Area in Nebraska.

Travelling from Eilat to Kiryat Shmonah (via Route 90 up the Jordan Valley), your halfway stop would be just south of the Ein Gedi nature reserve (but before you cross the bridge over Nahal Arugot), 146 miles from your start and 146 more miles to go.  

According to the Talmud (קידושין ל,א) that we happened to study a week ago,  the middle letter of the Torah is the Vav of the word Gichon, (גחון) found in פרשת שמיני – Leviticus 11:42. We noted that this traditional halfway point is way off. The actual middle letter of the Torah is letter # 152,403, the first letter of ויקרא פרק ח פסוק כט, which is 4,833 letters sooner than the traditional one.

Where is the Middle of the Torah?
	According to the Talmud	According to the Facts
Middle Letter of the Torah	וא"ו דגחון ויקרא 11:42	וא"ו דויקח ויקרא 8:29
Middle Words of the Torah	דרש דרש ויקרא 10:16	יצק אל ויקרא 8:18

Pagination in the Talmud

Are we making too much of this halfway page, this daf at the center of the Talmud Bavli? Perhaps. If you were to read the Vatican's 1381 manuscript of Kiddushin (shown below) you would see a completely different pagination, and today's daf would not be the halfway point.   

Manuscript of Talmud Bavli, Kiddushin, from the Vatican Apostolic Library (Vat.ebr.111/0222). The beginning of page 39a of the standard talmud in use today is show in red. This is one of three manuscripts in the Vatican Library together comprising all of Seder Nashim. It was copied by Yehoshaya b. Abraham b. Berechiah
b. Abraham b. Joseph of the Joseph Ha-Meoni family for Berechiah b. Mattathias and was completed on 11 Shevat 5141, or January 7th, 1381. Here is the entire colophon:

אני יהושעיה בן הרב ר' אברהם בן הרב ר' ברכיה בר' אברהם בר' יוסף ממשפחת יוסף המעוני כתבתי סדר נשים זה לר' ברכיה בר' מתתיה וסיימתיו בי"א יום לחדש שבט קמ"א לפרט המקום יזכינו
.להגות בו בניו ובני בניו עד סוף כל הדורות. אמן אמן. ברוך הנותן ליעף כח ולאין אונים עצמה ירבה

And below is our page, this time from a hand-written Talmud belonging to the Jewish Theological Seminary in New York. It dates from 1700; clearly the scribe undertook a labor of love in writing this when printed texts were widely available. And in this unique Talmud, Kiddushin 39 is not the middle page.

Talmud Kiddushin,1700.  Page 39a (לט)  is marked. From the Library of The Jewish Theological Seminary, New York, Record # 000009185.

So yes, this page is perhaps nothing more than an interesting by-product of the winning format in which the Talmud is now reproduced.  But we celebrate marathons and half-marathons, even though their length is totally arbitrary, (based on the length of the Marathon in the 1908 London Olympics - 26 miles, 385 yards; 26 miles because, well, who knows, and 385 yards being added so that the race would finish in front of the Royal Box). Running a half-marathon is a remarkable achievement, and so too is studying half of all the pages in the Babylonian Talmud. Congratulations to all who have achieved this milestone. But this is not an opportunity to relax: Don’t you have a sukkah to build?

According to The New York Times (April 6, 2016, p3.) there are 5,422 pages in the Talmud. Which is sort of correct.  And sort of not.  In our standard pagination of the Talmud, one page is made up of the verso and recto (a and b sides) sides. So Daf Yomi according to The Times would take twice as long as it does currently. Another way to look at it is that The New York Times prefers Amud Yomi to Daf Yomi.

From the Talmudology Archives - On the Healing Power of Honey, and Happy Rosh Hashanah

On Friday evening we will welcome in the start of the Jewish New Year. Among the many traditional foods that are eaten, honey features prominently. Many of us will dip our apples and our challah in it, as we symbolically wish for a sweet new year (and let’s face it, we really need one of those). So in honor of Rosh Hashanah, let’s dig into the Talmudology archives and talk about…honey.

In the Talmud we learn that aside from being delicious, honey was once used as a salve to heal a wound:

שבת עז,ב

דְּבַשׁ כְּדֵי לִיתֵּן עַל הַכָּתִית. תָּנָא: כְּדֵי לִיתֵּן עַל פִּי כָתִית. בָּעֵי רַב אָשֵׁי: ״עַל כָּתִית״ — אַפּוּמָּא דְּכוּלַּהּ כָּתִית, אוֹ דִילְמָא אַמּוּרְשָׁא קַמָּא דְּכָתִית, לְאַפּוֹקֵי הוּדְרָנָא דְּלָא — תֵּיקוּ

We learned in the mishna: The measure that determines liability for carrying out honey is equivalent to that which is used to place on a sore caused by chafing. A tanna taught in a Tosefta: The precise measure is equivalent to that which is placed on the opening of a sore, i.e., on the wound itself. Rav Ashi raised a dilemma: Does the term on a sore mean the measure of honey spread on the opening of the entire sore; or, perhaps it means the measure spread on the primary protuberance of the sore, to the exclusion of the surrounding area upon which he does not spread honey? No resolution was found for this dilemma either. Therefore, let it stand unresolved.

But elsewhere in the Talmud, honey was considered to be bad for a wound:

בבא קמא פה,א 

כדתניא הרי שעבר על דברי רופא ואכל דבש או כל מיני מתיקה מפני שדבש וכל מיני מתיקה קשין למכה והעלה מכתו גרגותני יכול יהא חייב לרפאותו ת"ל רק

It was taught in a Braisa: If the victim of an assault disobeyed the advice of his doctor and ate honey or all types of sweets - and this violated his doctor's instructions because honey and all types of sweets are harmful for a wound - it could be thought that the assailant is still obligated to heal the victim. Therefore the Torah uses the word רק (only) to teach otherwise...(Bava Kamma 85a)

Secretions of the honey bee. From Israili, Z. Antimicrobial Properties of Honey. American Journal of Therapeutics 2014. 21; 304–323.

But certainly according to the Talmud in Shabbat, honey was considered to be beneficial. In fact honey has been used as a medicine for at least the last 3,000 years.  And as we will see, honey has some quite amazing therapeutic uses.

FROM WHERE DOES HONEY COME?

The honeybee is the only insect that produces food eaten by humans. Here is what happens: The female honeybees use their proboscis (a tube-like tongue) to up suck flower nectar and mix it with their saliva and enzymes. Then they store it in a honey sack. Back at the hive, the mixture is regurgitated into cells, dried to about 16% moisture, and stored as a primary food source. As you might expect, the content of the honey depends on a number of factors including the species of bee, the kind of flowers on which they fed, and the conditions in which the honey was stored.

Honey as an Antibiotic

In a recent review article that focuses on the antimicrobial properties of honey, Zafar Israili from the Emory School of Medicine noted that a large number of laboratory and clinical studies have confirmed the broad-spectrum antimicrobial properties of honey.  These include antibacterial, antifungal, antiviral, and antimycobacterial.  “Honey,” wrote Israili, “was found to be an effective topical treatment for ringworms, athlete’s foot, jock itch, nail fungus, and yeast infections and reported to be comparable to many over-the-counter antifungal preparations.” These properties are likely due to the honey’s acidity, osmotic effect, high sugar concentration, and the presence of chemicals like hydrogen peroxide, antioxidants, and lysozymes.  

Honey contains more than 600 compounds (you can see a list of them here), and the wound healing properties of honey are probably its oldest and best studied medicinal property.  It has been shown to aid wound healing in conditions such as chronic pressure sores, traumatic and diabetic wounds, diabetic foot ulcers, boils, burns, fistulas, necrotizing fasciitis, and a very nasty condition called Fournier’s gangrene. (That's necrosis of the scrotum. Yes, quite gross.) So in contrast to the advice of the talmudic doctors that "honey is bad for an injury", honey turns out to be rather good for wounds, especially when applied directly to them.  But honey isn't just good for wounds...

“There is a large body of evidence to support the use of honey as a wound dressing for a wide range of types of wounds. Its antibacterial activity rapidly clears infection and protects wounds from becoming infected, and thus it provides a moist healing environment without the risk of bacterial growth occurring. It also rapidly debrides wounds and removes malodor.”

— Molan, PC. The Evidence supporting the use of honey as a wound dressing. Lower Extremity Wounds 2006. 5 (1); 52.

Your Mother was correct

A 2012 study from physicians at the Sackler School of Medicine in Tel Aviv tested the effects of honey on nocturnal cough and sleep quality.  They enrolled 150 children age 1-5 years (and presumably, their tired and exasperated parents) and half an hour before bedtime, gave half of them “a single dose of 10g of eucalyptus honey, citrus honey, or labiatae honey,” and the other half a placebo. (In case you were wondering, as was I, as to what the placebo was, here’s the answer: date extract, “because its structure, brown color, and taste are similar to that of honey.” True enough.) What they found might change the way you treat your own cough this winter. Each of the three honey groups had a better response compared with the date extract, and no significant differences were found among the different types of honey. The authors concluded that honey may be preferable to cough and cold medications for childhood respiratory infections. 

The effect of different types of honey and date extract on cough frequency (I), cough severity (II), cough bothersome to child (III), the child’s sleep (IV), parent’s sleep (V), and combined symptoms score (VI). P <0.05 for the comparisons between group D and the other groups. A, eucalyptus honey; B, citrus honey; C, labiatae honey; D, silan date extract. From Cohen, AH. et al. Effect of Honey on Nocturnal Cough and Sleep Quality: A Double-blind, Randomized, Placebo-Controlled Study. Pediatrics 2012. 130 (3); 465-471.

Honey as a Medicine for Pretty much everything

There are dozens of other medical conditions for which honey may be used. Here is what the review from Israili has to say:

Honey has been reported to be of benefit in a large number of human pathologies including allergy, asthma, bronchitis, common cold, flu, hay fever, nasal congestion, rhinitis, sinusitis, upper respiratory infections, sore throat, cough, fatigue, anxiety, migraine (stress related), cuts, lacerations, burns, wounds (venous, arterial, diabetic, malignant), pressure ulcers, malignant ulcers, perianal and gluteofemoral fistulas, bed sores, adult and neonatal postoperative infections, necrotizing fasciitis, pilonidal sinus, insect bites, infections (bacterial including antibiotic-resistant strains and fungal), septicemia, conjunctivitis and other eye diseases, endophthalmitis, acne, chronic seborrheic dermatitis, dandruff, eczema, psoriasis, inflammation, gingivitis, stomach ache, stomach ulcers, digestive disorders, constipation, vomiting, diarrhea, colitis, dehydration, diabetes, osteoporosis, insomnia, chronic fatigue syndrome, anemia, hypertension, immune disorders, multiple sclerosis, cardiovascular disease, hepatitis, tumors, cancer, and radiation/chemotherapy-induced oral mucositis.

You'd have to check the references and decide if the evidence supports claims like this. But in any event, this list supports the observation in the Talmud that honey was used to heal wounds. And now we use it to usher in our hopes and prayers for a safe and sweet new year.

***

Want more Talmudology on honey? Click here on how to melify a corpse, and honey as a preservative. But don’t share it when your’re eating, ok?

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SHannah TovaH From Talmudology

Kiddushin 30a ~ How Many Letters are in a Sefer Torah?

קידושין ל, א

לפיכך נקראו ראשונים סופרים, שהיו סופרים כל האותיות שבתורה, שהיו אומרים: וא"ו דגחון חציין של אותיות של ספר תורה, דרש דרש  חציין  של תיבות, והתגלח של פסוקים

Therefore the early sages were called "counters" - soferim - because they counted all the letters of the Torah. They used to say: the letter vav of the word Gachon (Lev.11:42) is the half-way point of the letter of a Torah. The words "darosh darash" (Lev. 10:16) represent the half way point of the number of words in the Torah. The verse that begins with the word "Vehitgalach" (Lev.13:33) is the half way point of the number of verses in the Torah...

Today's page of Talmud in the Daf Yomi cycle covers some important material for those interested in the way in which Judaism and science interact.   The business of counting the letters in the Torah was apparently taken very seriously - so much so that one of the names by which the rabbis of the Talmud were known  - soferim - means "those who count."  To this day, the person who handwrites a Sefer Torah is called a counter (סופר), and not a writer (כותב). The Talmud emphasizes that this counting exercise was taken so seriously that the letters, words and verses were counted, and counted again. 

קידושין ל, א

בעי רב יוסף וא"ו דגחון מהאי גיסא או מהאי גיסא א"ל ניתי ס"ת ואימנינהו מי לא אמר רבה בר בר חנה לא זזו משם עד שהביאו ספר תורה ומנאום

Rav Yosef asked a question: This letter vav of the word Gachon, is it part of the first half or part of the second half of the letters of the Torah? They said to him, "let us bring a Torah scroll and count! For didn't Rabbah bar bar Channah say in a similar context: "They did not move from there until they brought a Torah scroll and counted all its letters"...

The View of Tradition, And OF the Journal Tradition

Writing in Tradition in 1964, the late scholar Louis Rabinowitz (d. 1984) asked how Orthodox Jews should regard the text of the Torah , "...upon which depends the whole enduring magnificent structure of the Oral Law and the Halakhah, in comparison with those texts which show variants from it?"  Here is his reply:

“The answer is surely simple and logical. “The early scholars were called Soferim,” declares the Talmud (Kid. 30a) “because they were wont to count (soferim) all the letters of the Torah.” The meticulous manner in which they carried out this task is sufficiently indicated in the same passage by the information which it elicited to the effect, for instance, that the vav of gachon (Lev. 9:42 - [sic]) marks the half-way mark of the letters of the Torah, the words darosh darash of Lev. 10:16 the dividing line between the words...


With what loving care and sacred devotion, then, did they jealously guard every letter of the text! What exhaustive and detailed regulations they laid down in order to ensure that the copying of the scrolls should be completely free from human error! There has been nothing like it in the history of literature or religion, and in this respect the Massoretic text stands indisputably in a class by itself.”

— Louis Rabinowitz. Torah Min Ha-Shamayim.Tradition: A Journal of Orthodox Jewish Thought, 1964-5: 7;1: 34-45

Leaving aside the ironic typographic error that mis-references the location of the vav of Gachon, was the late rabbi Rabinowitz correct in remarking on the "loving care and sacred devotion," with which "they jealously guard every letter of the text"?

So how many letters are there in a Torah?

There are varied counts given for the number of letters in the Torah, but a couple of results seem to be most popular.

• 304, 805 From here, and here and here, and from Even-Shoshan (see below).

• 304,801 From here.

One website shares the source code used to count the words and letters in Torah; its results are shown below, and are off by four when compared to others who claim to have counted.

Letters and Words in the Torah
	Words	Letters
בראשית	20,614	78,063
שמות	16,714	63,527
ויקרא	11,950	44,790
במדבר	16,408	63,529
דברים	14,295	54,892
TOTAL	79,981	304,801

And How Many Verses Are There?

The same website gives a count of 5,844 verses in the Torah.  Rabbi Yair Chaim ben Moses Bachrach (d. 1702), author of the Chavot Ya'ir, notes that there are 5,845 verses in the chumashim he used. But today's daf of Talmud records that there are 5,888 verses. And here is the count from Even-Shoshan's קונקורדנציה חדשה (New Concordance of the Bible):

From Even-Shoshan (ed.) A New Concordance of the Bible. Kiryat Sefer, Jerusalem 1987.

Side-Bar: From Where did Even-SHoshan Get his word count?

Even-Shoshan lists his reference as Rabbi Chaim Mordechai Brecher, who published a Yiddish translation of the entire Hebrew Bible. (Brecher was born in what is now Ukraine in 1880 and died in New York in 1965.  His Yiddish translation was published in New York in 1941, and was republished six times, the last in 1957.)  At the end of the second volume of his translation (p. נא), R. Brecher addressed the thorny question of the letter and word counts in our Torahs, and had this to say:

The truth is, this [question of how many words there are in a Sefer Torah] is astonishing, and I couldn't rest because of it. So I decided to count them, and I, myself, counted all the words in the entire Torah. In order to make it clear to the reader that I didn't make a mistake in my count, I am here providing a list of all the verses in all the chapters as they are currently divided...My count is correct. As the ancient wise men say: Love Plato, love Aristotle, and love the truth most of all.

R. Brecher's total word count is 79,976 (although this count actually comes from here) - and so his half way point in the Torah is word #39,988. 

The Misplaced Middle of the Torah

Now back to today's page of Talmud. According to it, the middle letter of the Torah is the Vav of the word Gachon, (גחון) found in פרשת שמיני. However this claim is way off. Since there are about 304,805 letters in the Torah scrolls in use today, (I say about because of what we have just noted regarding the precise count,) the middle letter would be letter # 152,403, the first word of this verse (Lev 8.29):

ויקרא פרק ח פסוק כט 

ויקח משה את החזה ויניפהו תנופה לפני יקוק מאיל המלאים למשה היה למנה כאשר צוה יהו–ה את משה 

However the Vav of the word Gichon, is letter #157,236 - off by 4,833 letters. Oy.

It's no better regarding the words. If we go with the actual word count as being 79,980, then the middle words are # 39,990 and #39,991. These are the words יצק אל in verse below (Lev. 8:18):

ויקרא פרק ח פסוק טו 

וישחט ויקח משה את הדם ויתן על קרנות המזבח סביב באצבעו ויחטא את המזבח ואת הדם יצק אל יסוד המזבח ויקדשהו לכפר עליו

But the middle words of the Torah, according to Today's daf, are דרש דרש found over 900 words later (Lev.10:16):

ויקרא פרק י פסוק טז 

ואת שעיר החטאת דרש דרש משה והנה שרף ויקצף על אלעזר ועל איתמר בני אהרן הנותרם לאמר

That's a lot of letters to miscount, especially if your name is "the counter." Several suggestions have been made to address these discrepancies:

1.  The text of the Torah that the rabbis of the Talmud were using was significantly different to the one we use today.  This is possible, but then why does the Talmud never cite of any of these extra words and verses? The discrepant count is about 3% - that's a lot of missing text.

2.  The rabbis in the Talmud were not good at math. Again, possible, but the Talmud claims that they took the counting so seriously that they were called COUNTERS. It also claims that they undertook the counting exercise on several different occasions.  Were they really that bad at math?

3. The rabbis in the Talmud didn't mean this count to be taken literally. While many apologists like this answer, it is at total odds with the text. The Talmud states: they counted.

4.  The rabbis guesstimated the count. Perhaps the rabbis never really counted, but guessed at where the middle of the Torah lay: somewhere in the middle of the middle of the Five Books. After that, the letter vav of the word Gachon became the official midpoint, even though it was not accurate.  The problem with this suggestion is again, that the Talmud states that the soferim actually counted, and counted again. Not that they guessed, and guessed again.  

Science, Math and Judaism

Of all the scientific disciplines, it is mathematics that is first introduced to us. We teach toddlers to count, sometimes before they can even walk, and we all pursue some kind of mathematical training through high school.  Unlike medicine or physics or biology or astronomy, mathematics is something we all do, to some degree.  And we all understand what counting means.  This passage in the Talmud is the most readily understandable example of a conflict between science and Judaism. It is a conflict in which the basic text of rabbinic Judaism declares a fact that is, well, just not a fact.  Some find this conflict to be so intellectually troubling that their only path is to reject Jewish practice. Others, equally aware of the conflict, are comfortable with their intellectual position in which the scientific inaccuracies of the Talmud require no wholesale rejection of Jewish practice. Where do you fit on this spectrum, and, perhaps more importantly, what can you do to engage in a respectful dialogue with those whose opinions on these matters are not your own?

Kiddushin 29a ~ Swimming and Drowning

קידושין כט, א

האב חייב בבנו למולו ולפדותו וללמדו תורה ולהשיאו אשה וללמדו אומנות וי"א אף להשיטו במים רבי יהודה אומר כל שאינו מלמד את בנו אומנות מלמדו ליסטות ליסטות ס"ד אלא כאילו מלמדו ליסטות

With respect to his son, a father is obligated to circumcise him, to redeem him [if he is a firstborn], to teach him Torah, to marry him off, and to teach him a craft.  Some say, he is also obligated to teach him to swim...(Kiddushin 29a)

Every year, according to The World Health Organization, more than 5,000 children drown in Europe. And for every child who drowns (the majority of whom are under five years of age) at least two others suffer lifelong neurological disability.  

Average standardized mortality rates for drowning in children aged 0–19 years in the WHO European Region, 2003–2005 or most recent three years. From The European Report on Child Injury Prevention. World Health Organization 2008.

In the United States, there are an average of ten drowning deaths each day. Of the more than 3,500 people who drown each year in the US, about a fifth are children under the age of 14.  And here are some other facts that may surprise you about drowning in the US, courtesy of the Centers for Disease Control:

• Nearly 80% of people who die from drowning are male.

• Children ages 1-4 have the highest drowning rates. In 2009, among children 1-4 years old who died from an unintentional injury, more than 30% died from drowning.

• Among children ages 1-4, most drownings occur in home swimming pools.

• Drowning is responsible for more deaths among children 1-4 than any other cause except congenital anomalies (birth defects).

• Between 2005 and 2009, the fatal unintentional drowning rate for African Americans was significantly higher than that of whites across all ages.  The disparity is widest among children 5-14 years old. The fatal drowning rate of African American children ages 5-14 is almost three times that of white children in the same age range.

• The disparity is most pronounced in swimming pools; African American children drown in swimming pools at rates 5.5 times higher than those of whites.  

New data on drowning trends

In 2019, two Taiwanese epidemiologists published a study that assessed international drowning mortality rates over the past decade. The news was mixed. Among the 61 countries they studies, 50 had managed to reduce their drowning fatalities. And some that previously had a high rate of drowning deaths, like Lithuania, Moldova, Kyrgyzstan, Romania, El Salvador, also showed a significant decrease. In Israel, there were 93 drownings in 2004-2005, a rate of 6.7 per 100,000 people. And in 2015-2016 there were 83 deaths, a drop in the rate to 4.7 per 100,000 people - a 29% reduction. In the US the rate also dropped, from 11.8/100,000 to 10.7/100,000, which was a more modest decrease of only 10%.

From here.

How We Drown

Unlike the movie depiction of a person loudly flailing as he tries to stay afloat, the process of drowning is actually very quiet; there is usually no noise and little to see.

Once the victim disappears under the surface, the oxygen content of the blood rapidly decreases and unconsciousness follows quickly. In most cases water enters the lungs and results in wet drowning. This causes constriction of the blood vessels in the lungs (and for the medically curious among you, hypertension with a ventilation/perfusion mismatch, aggravated by surfactant destruction and washout, decreased lung compliance and atelectasis. Acute respiratory failure is common.There. Now you know.)  But in 10–20% of deaths from drowning, a small amount of water entering the larynx causes persistent spasm, which results in choking and an immediate outpouring of thick mucus, froth and foam, but without significant aspiration; this is called dry drowning.

What's more Dangerous - a swimming pool or a gun?

The dangers of children drowning is real. So real that it turns out that owning a pool is more dangerous that owning a gun. (Notice to readers outside the US: you can own a gun here...) Dunber and Levitt, in their wildly popular 2005 book Freakonomics (p135-6) explained why this is so:

Consider the parents of an eight-year-old girl named, say, Molly. Her two best friends, Amy and Imani, each live nearby. Molly's parents know that Amy's parents keep a gun in their house, so they have forbidden Molly to play there. Instead, Molly spends a lot of time at Imani's house, which has a swimming pool in the backyard. Molly's parents feel good about having made such a smart choice to protect their daughter.

But according to the data, their choice isn't smart at all. In a given year,there is one drowning of a child for every  11,000 residential pools in the United States. In a country with 6 million pools, this means that roughly 550 children under the age of ten drown each year.) Meanwhile, there is 1 child killed by a gun for every1 million-plus guns. In a country with an estimated 200 million guns, this means that roughly 175 children under ten die each year from guns.The likelihood of death by pool (1 in 11,000) versus death by gun (1 in 1 million - plus ) isn't even close: Molly is far more likely to die in a swimming accident at Imani's house than in gunplay at Amy's.

A Common Sense Halacha?

In his commentary on the Mishnah, Maimonides counts the command to teach a child to swim as one of the duties incumbent on a parent (or, more precisely, on a father). 

פירוש המשנה לרמב"ם מסכת קידושין פרק א משנה ז 

 מצות הבן על האב שש מצות ואלו הן, למולו ולפדותו וללמדו תורה ולהשיאו אשה וללמדו אומנות ולהושיטו בנהר. ולמדו לכולם מן הכתובים בראיות שיארך ביאורם כאן ואין תועלת מרובה בכך, כל אלו חייב האב לעשותם לבן, ואין האם חייבת לעשותם לבנה והוא ענין אמרם האנשים חייבין והנשים פטורות

There are six duties incumbent on a father towards his son: 1) to circumcise him; 2) to redeem him [from a Cohen if he is a firstborn]; 3) to teach him Torah; 4) to marry him to a woman; 5) to teach him a trade and 6) to teach him to swim...A father is required to do each of these things, but a mother is not required to teach them to her daughter, for this is one of those things that fall into the category of "men are obligated and women are exempted"... 

However in his Mishnah Torah, Maimonides did not include the obligation to teach swimming, and this obligation is also omitted in the sixteenth century normative Shulchan Aruch. There is no obvious reason for this omission, though this question would make a great topic of conversion at your Shabbat table tonight. But not everything that makes sense needs to be part of the code of Jewish Law. It can just be...a sensible thing to do.  Perhaps there is no better example of this than a parent, (mother or father) teaching their child, (son or daughter,) to swim.  

“As a father who has lost a son, I know first-hand the unbearable pain that comes with a child’s death. Amidst my grief, I am able to take some small solace in the fact that everything possible was done to fight the disease that took my son’s life. If my son had died in a backyard pool due to my own negligence, I would not even have that to cling to. Parents who have lost children would do anything to get their babies back. Safeguard your pool so you don’t become one of us.”

— Steven Levitt, co-author of Freakonomics. "Pools more dangerous than guns". Chicago Sun-Times 7/28/2001