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Parsha Halacha – Parshat Bo

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Parsha Halacha is underwritten by a grant from Dr. Stephen and Bella Brenner in loving memory of Stephen’s father, Shmuel Tzvi ben Pinchas, and Bella’s parents, Avraham ben Yitzchak and Leah bas HaRav Sholom Zev HaCohen.

The Torah portion of Bo ends with various mitzvot that we are commanded to perform in order to remember the exodus. One of these is the mitzvah of Tefillin[1] as it says (Exodus 13:9), “And it shall be to you as a sign upon your hand[2] and as a remembrance between your eyes, in order that the law of the L-rd shall be in your mouth.”
The Ramban explains that by writing about the Exodus (in the Tefillin) and placing it on one’s arm and head, one will remember the Exodus constantly. He will thus recognize G-d as his master who freed him from bondage and will therefore study His Torah and observe His mitzvot.
Several verses later it says (verse 16), “And it shall be for a sign upon your hand and for ornaments between your eyes, for with a mighty hand did the L-rd take us out of Egypt.”
In the second verse, the Torah writes יָ֣דְכָ֔ה (your hand) with an extra ה. Our sages (Menachot 37b) interpret this to mean יָד כֵּהָה ,  i.e., that the Tefillin should be placed on the hand that is weaker. The word כֵּהָה   means weak as seen from the following verse (Levit. 13:6) וְהִנֵּה֙ כֵּהָ֣ה הַנֶּ֔גַע which means, “Behold, the color of the lesion has dimmed (i.e., gotten weaker). Rashi (on the Talmud ibid) writes that יָ֣דְכָ֔ה with an extra ה is a feminine form of the word. This alludes to the weaker hand as females are usually weaker than males.
Some sages say that the word יָ֣דְכָ֔ה teaches us that even one who has no functioning hand (יָד כֵּהָה indicates that the hand was crushed or otherwise injured) must still place the Tefillin on the upper arm. (One who, G-d forbid, has no upper left arm need not put on the hand Tefillin at all but only puts on the head Tefillin.) These sages cite other sources that point to the fact that the Tefillin should be placed on the left arm.
·        Arm Means Left
There are several verses in the Torah that indicate that the word יָד (hand or arm) refers to the left hand unless otherwise specified.[3] For example (Isaiah 48:13), ““Even My hand [yadi] has laid the foundation of the earth, and My right hand [viyemini] has spread out the heavens.” Since the hand mentioned in the second part of the verse is the right hand, the hand (יָד) mentioned in the first part of the verse must be the left hand. Similarly, the verse (Judges 5:26) describing how Yael killed the Canaanite general Sisra says, “Her hand [yadah] she put to the tent pin, and her right hand [viyeminah] to the workmen’s hammer.” Finally, in Tehillim (74:11) King David writes, ““Why do You withdraw Your hand [yadkha], even Your right hand [viyeminecha]? Draw it out of Your bosom and consume them.”[4]
·        The Writing Hand is the Binding Hand
Another interpretation is based on the verses about Tefillin in Deut. 6:8 and 9. In one verse it says, “And you shall bind them for a sign upon your arm,” and in the next verse it says, “And you shall write them upon the doorposts of your house.” This indicates that the same hand used to write should be used to bind the Tefillin. Since, generally, one uses the right hand to write, that is the hand he must use to bind his Tefillin. If one is using the right hand to bind (tie or wrap) the Tefillin, he must clearly be wrapping them on his left arm.
Why the Left?
  • G-d’s Might
The Ohr HaChayim explains that the right hand represents G-d’s loving kindness while the left represents His strength and might. Since He used his strength and might to punish the Egyptians at the time of the Exodus, we recall this by placing the Tefillin on the left arm.
  • Overcoming Corporality
The Kli Yakar explains that the right (more dominant) side represents one’s corporal desires as they are extremely powerful. The left (and weaker) side represents one’s intellectual awareness which is not as powerful as one’s instinctive desires. The right side of a person’s body contains the liver which represents corporality (as it has a very physical function); thus the right arm is more powerful. The left side of a person, on the other hand, contains his heart which is traditionally related to one’s intellect and feelings. This is why the left arm is weaker than the right. The point of the exile in Egypt was to help us minimize our corporality and maximize our intellectual powers which are instrumental in serving G-d. The Tefillin are placed on the left arm which is over the heart as they are supposed to impact our feelings and intellect and turn them towards G-d. For the same reason, they are also placed on the head above the brain. We are told to place them between the eyes since the eyes can easily lead us to sin and the Tefillin should rein in these desires.
  • G-d’s Right
Some say[5] that we place our Tefillin on the left arm as this corresponds to G-d’s right side (considering that He is facing us).
  • To Overcome the Yetzer Hara
The heart represents our seething desires – those associated with our evil impulse, the Yetzer HaRa. By placing the Tefillin on the left side which is closer to the heart, we indicate that we are subjugating our desires and emotions – to the service of G-d.[6]


The Talmud says that left handed people should put Tefillin on their right arms.[7] This is based on the abovementioned verses from which we learn that for most people Tefillin is placed on the left arm.
·        If this is derived fromיָד כֵּהָה  (the weaker hand), then certainly the right hand of a lefty is the weaker one.
·        If we derive it from the comparison between the writing and the binding, since a lefty writes with his left hand, he should also use his left arm to bind the Tefillin onto his right arm.
·        If we derive it from the fact thatיָד   means the left hand, we can also derive that a lefty should place the Tefillin on his right arm as the Torah uses the word שמאל (left) to mean weaker and the word ימין to mean stronger. As an example of this, the Talmud says אטר מניח תפילין בימינו שהוא שמאלו which means that a leftie should place the Tefillin on his right hand which is his left (weaker) hand.[8]


The Talmud days that one who is ambidextrous (i.e., he uses both his right and left hand) should put his Tefillin on his left hand as this is the hand which is weaker for most people.
Writes with One Hand and Uses the Other One for Everything Else
If a person writes with one hand but does everything else with his other hand, there is an argument as to which hand he should use for Tefillin. (See Tosfot D.H. Mah Ketivah in Menachot ibid that poses this question.) If we follow the opinion that one should place the Tefillin on the weaker arm, one should place the hand Tefillin on the arm with which he writes since this is, after all, the weaker one. If, on the other hand we are following the opinion that one must use his writing hand to bind the Tefillin on the opposite arm, one should place the Tefillin on the arm with which he does not write as he can then use his “writing hand” to bind the Tefillin on that arm. In practice the Shulchan Aruch (A.C. 37) rules that one should put the Tefillin on the arm with which one does not write, and the Shulchan Aruch Harav concurs with this ruling. I.e., the writing hand is considered the stronger one for the purpose of Tefillin.
The Tzemach Tzedek (O.C. Responsa 4:2 and 12:3) writes that one who writes with his right hand but does everything else with his left should put Tefillin on both arms (not at the same time). Whereas one who does most everything with his right hand and the only thing he does with his left hand is write, should put the Tefillin on his left arm. The reason for this is that such a person might be considered ambidextrous in which case the Tefillin should be placed on the left arm. In addition, since the left arm is the correct one for most people, we place it on this arm in cases of doubt.[9]

Chabad Custom

In practice the Chabad custom is as follows.[10] One who writes with his left hand but does everything else with his right hand should first put the hand Tefillin on his right arm and wear them in that position during davening. After davening he should remove it from the right arm, place them on the left arm (while keeping on his head Tefillin) and say the Shema while wearing it in that position. (There are two methods of how to switch Tefillin made for one arm, to the other. This is beyond the scope of this article.)  In this way, one is fulfilling both the ruling of the Alter Rebbe and that of the Tzemach Tzedek.
One who writes with their right hand and does everything else with their left hand should place the Tefillin on their left arm for the duration of davening and then switch it to the right arm afterwards and recite the Shema as above. In this way he is following both the ruling of the Alter Rebbe (who says to place it on the left arm) and that of the Tzemach Tzedek (who says to place it on one arm and then on the other).
In either case, when putting on the hand Tefillin before davening one should bear in mind that the blessing is also “covering” the second placement of the hand Tefillin, which will be done after davening. (It would seem that one should not interrupt between taking it off of one arm and placing it on the other. Rather one should do so immediately.)

Ashkenaz Custom

In the above cases, the general custom of Ashkenazim is to place the Tefillin on the arm with which one does not write. I.e., whichever arm he writes with is considered the stronger one for the purpose of Tefillin and he places it on the opposite arm.[11]

Sefardic Custom

The Yalkut Yosef writes (Siman 27) that the main halacha for Sefardim is to place the Tefillin on the hand which is not used for writing even if it is, otherwise, the stronger hand. However, it is best to place the arm Tefillin on the other arm after davening for the recital of Shema (as mentioned above regarding the Chabad custom) in order to fulfill the other opinion. One who wears Rabeinu Tam Tefillin should also place the Tefillin on both arms (one after the other).
May we Merit to Conquer our Yetzer HaRa and Serve G-d with Sincerity
[1] Look here https://collive.com/army-chief/ for an amazing story relating to Tefillin.
[2] The Rashbam writes that on a simple level the verse can be interpreted to mean that one should remember the exodus constantly as if it were written on one’s hands and forehead as the verse says (Song of Songs 8:6), “Place me like a seal on your heart, like a seal on your arm…” Similarly, King Solomon writes (Mishlei 3:3), “Kindness and truth shall not leave you; bind them upon your neck, inscribe them upon the tablet of your heart.”
The Ibn Ezra says that one cannot compare Mishlei (and the Song of Songs) which were written as parables, with the Five Books of Moshe which should be interpreted in a straightforward manner unless it is clearly only a parable.
[3] See Ma’adanei Yom on the Rosh, Hilchot Tefillin 18:100 (quoted in the Metivta Shas) as to why the Talmud finds it necessary to quote.
[4] In the Talmud, Rabbi Yossi HaChorem disagrees with the premise that in the Torah “yad” means the left hand based on the verse (Gen. 48:17), “And Joseph saw that his father was placing his right hand יַד־יְמִינ֛ו)ֹ) on Ephraim’s head…” where clearly “yad” means the right hand. He therefore must learn that Tefillin is placed on the left from one of the other methods.
[5] Sefer Emunah UBitachon quoted in the footnotes on Rabeinu Bcahaye (Moosad HaRav Kook) on this week’s parsha.
[6] Or Yitzchak by Rabbi Yitzchak of Radvil, son of Reb Yechiel Michel of Zlotchov. Parshat Bamidbar, page 259b
[7] See Piskei Teshovot 27:12 and note 98 that some Rishonim and many Kabbalists were of the opinion that even left handed people should place their Tefillin on their left arms. This opinion is not accepted in practice.
[8] The Mordechai and Vilna Gaon as explained in the Metivta Shas
[9] It is noteworthy that that the Tzemach Tzedek does not quote his grandfather’s opinion (the Shulchan Aruch HaRav) in these Responsa.
[10] See Hebrew footnote 60 in the new Shulchan Aruch HaRav, Siman 27 based on Igrot Kodesh vol. 11 pg. 148
[11] But see Igrot Moshe O.C. 4:11 who writes that in the cases discussed above (one who writes with one hand but does everything else with the other) the Tefillin should be placed on the left arm. This follows the opinion of several Rishonim and that of the Bach.
Wishing you a Shabbat Shalom UMevorach!

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