OPINIONS: The Gemara says that a left-handed person is supposed to wrap his Tefilin on his right arm. There are three basic opinions among the Rishonim with regard to who is considered left-handed. The three opinions are based on the different Derashos recorded in the Gemara here which teach that Tefilin should be worn on the left arm, and which imply that a left-handed person wears Tefilin on his right arm. (Although the Gemara earlier (36b) cites several verses that teach that the word "Yad" means the left arm, and thus when the Torah says that Tefilin are to be worn "Al Yadecha," it means that Tefilin must be worn on the left arm, from those verses one might have thought that Tefilin must always be worn on the left arm, even by a left-handed person.)

(a) RABEINU YECHIEL maintains that the hand with which one writes determines whether he is right-handed or left-handed. Hence, one who writes with his left hand is considered left-handed. This opinion is cited by the SHULCHAN ARUCH (OC 27:6).

This opinion is based on the Derashah of Rebbi Nasan. Rebbi Nasan derives from the proximity of the words "u'Keshartam" (Devarim 6:8) and "u'Chesavtam" (Devarim 6:9) that just as "Kesivah" (writing) is done with the right hand, the binding of Tefilin on the arm must be done with the right hand, which means that the Tefilin themselves are placed on the left arm (so that the right hand can wrap them).

Rebbi Nasan's Derashah implies that the Tefilin are to be placed on the arm opposite the hand with which one writes. It does not matter whether a person uses that hand for other activities; as long as he uses it to write, it is considered his dominant hand and he places the Tefilin on the opposite arm.

(b) The ROSH quotes the SEFER HA'TERUMAH who maintains that one wears Tefilin on the weaker arm, regardless of which hand he uses for writing. The stronger arm is defined by which arm he uses for most activities. One who does most activities with his left hand is considered left-handed, even if he writes with his right hand. This opinion is also cited by the Shulchan Aruch (ibid.). This is also the ruling of the VILNA GA'ON.

This opinion is based on the next Derashah in the Gemara, the Derashah of Rav Ashi. Rav Ashi learns from the word, "Yadchah" (Shemos 13:16), which is written with a "Heh," that the Tefilin are supposed to be placed on the weaker arm. (As Rashi explains, this is inferred either from the fact that "Yadchah" is written in the feminine form with a "Heh," and the feminine form denotes weakness, or from the reading of the word as "Yad Kehah," the "weak hand.") For most people, it is clear whether the right hand or the left hand is the stronger hand, and thus the Tefilin are placed on the opposite arm. In a case in which a person performs some activities with one hand and other activities with the other hand, the dominant hand is determined by which hand he uses for more activities (Rov). According to Rav Ashi, there is no special significance to writing with one hand or the other.

(c) The third opinion maintains that one is considered left-handed only if he writes and does most other activities with his left hand. This is the view of the BACH. The Bach argues with the Shulchan Aruch's understanding of the opinion of Rabeinu Yechiel. The words of Rabeinu Yechiel as quoted by the TUR are, "Only when one does all of his activities with the left hand [is he considered left-handed]. However, one who writes with his right hand, even though he does all other activities with his left hand, is considered like every other [right-handed] person." Rabeinu Yechiel discusses only a case in which writing is done with the right hand and other activities are done with the left. In such a case, he rules that the Tefilin are put on the left arm. Rabeinu Yechiel does not mention what the Halachah would be in the opposite case -- when one writes with his left hand and does all other activities with his right. The Shulchan Aruch assumes that Rabeinu Yechiel means that the hand used for writing is the dominant hand, whether it is the right hand or the left. However, if this is the intention of Rabeinu Yechiel, then he should write simply that one's dominant hand is the hand with which he writes, without mentioning anything about which hand he uses for all other activities. It seems from the words of Rabeinu Yechiel that one who writes with his left, but performs all other activities with his right hand, should put Tefilin on his left arm.

The Bach explains the basis for this approach. Although the Halachah follows the view of Rav Ashi who says that one puts Tefilin on the weaker arm, the Derashah of Rebbi Nasan is still correct as well. The Hekesh of "Keshirah" to "Kesivah" is a Gezeiras ha'Kasuv that teaches that although in most cases the weaker arm is determined based on which arm is used for doing most activities (and not based on which arm is used for writing), nevertheless if one writes with his right hand he must put Tefilin on his left arm, even though it is not his weaker arm (that is, he does most other activities with his left arm). This Gezeiras ha'Kasuv applies only to one who writes with his right hand. Although the wording of the Hekesh could be understood to apply also to one who writes with his left hand, the Gezeiras ha'Kasuv cannot apply to such a person because of Rav Ashi's Derashah. Therefore, it must be that the Gezeiras ha'Kasuv is intended only to teach that people who write with their right hands are considered to be right-handed. The Derashos are not applied in the opposite manner (to say that the Hekesh teaches that one who writes with his left hand should put Tefilin on his right arm, even though he uses his right arm for all other activities and it is not the weaker hand, and the Derashah of Rav Ashi teaches that one who writes with his right hand and does all other activities with his left hand should put Tefilin on his left hand), because it is logical to assume that the Torah is teaching that the Tefilin should be placed on the arm that is weaker for most people, which is the left arm (this is similar to the Gemara's logic in the case of a person who has equal dexterity in both hands, in which case the Gemara says that one should wear the Tefilin on the left arm like most people).

RAV MOSHE FEINSTEIN zt'l also learns that the Halachah is in accordance with both the Derashah of Rebbi Nasan and the Derashah of Rav Ashi. The general rule is that the Tefilin are placed on the weaker arm (Yad Kehah). However, the Hekesh of "Keshirah" to "Kesivah" teaches that extra significance should be given to the hand with which one writes, and that one who writes with his right hand must put Tefilin on his left arm even though he does all other activities with his left hand. This is not because only writing is important. Rather, it is because writing is equal to all other activities. Since it is equal to all other activities, one who writes with his right and does everything else with his left is considered ambidextrous, one who has equal dexterity in both hands, and the Gemara says that such a person puts Tefilin on the left arm. Naturally, one who writes with his left hand and does all other activities with his right hand will also put Tefilin on his left hand, because the verse implies that writing is only equal to, but not greater than, all other activities. Therefore, such a person is also considered one who has equal dexterity in both hands and must put Tefilin on his left hand.

The way that Rav Moshe Feinstein explains the application of both Derashos has an advantage over the Bach's explanation. According to Rav Moshe's explanation, there is no need to say that the Hekesh of "Keshirah" to "Kesivah" is a Gezeiras ha'Kasuv which teaches that the Tefilin are put on the stronger arm. According to Rav Moshe, the Hekesh teaches only that Kesivah, writing, is an important activity and is equal to all other activities combined. Once we know that, we can categorize a person who writes with his right hand and does everything else with the left as one who has equal dexterity in both hands who must put Tefilin on his left hand, as the Gemara says. Also, one who writes with his left hand and does everything else with his right hand will put Tefilin on his left hand because of the same principle. (Rav Moshe quotes the BI'UR HALACHAH who asserts that this is also the logic of the Bach, but the words of the Bach clearly do not express this logic.) (Mordechai Zvi Dicker)

QUESTION: The Gemara (37a) discusses a case of a firstborn baby boy who was born with two heads. How much money must his father give to the Kohen in order to fulfill the Mitzvah of Pidyon ha'Ben? A certain elder taught that ten Shekels (twice the amount of an ordinary Pidyon ha'Ben) must be given. The Gemara asks that the Halachah is that a child who is a Tereifah (he has a mortal defect) is exempt from Pidyon ha'Ben. A baby with two heads certainly is a Tereifah. The Gemara answers that the case of a baby with two heads is different, because the Torah itself says that the Mitzvah depends on the number of heads, as the verse says, "Chameshes Shekalim la'Gulgoles" -- "five Shekels per head" (Bamidbar 3:47), implying that a firstborn with two heads must be redeemed with ten Shekels.

How does the Gemara answer its question? A baby with two heads is still a Tereifah, and thus he should be exempt from Pidyon ha'Ben. The fact that the Torah says that one must pay "five Shekels per head" must mean that one pays five Shekels per living head. A baby with two heads is not going to live, and thus he should be exempt.

This question may be answered with RASHI's definition of Tereifah. Rashi explains that when the Gemara says that a Tereifah ("Nitraf") is exempt from Pidyon, it does not refer to a baby with a mortal defect. Rather, it refers to a baby that literally was "Nitraf" -- killed ("torn apart") within thirty days of his birth. A baby that was killed is exempt from Pidyon ha'Ben. Although a two-headed baby will likely die due to his mortal defect, if he lives past thirty days he no longer is in the category of "Nitraf" and he must be redeemed.

However, RABEINU TAM (quoted by TOSFOS) understands that when the Gemara says that a Tereifah is exempt from Pidyon, it refers to the normal meaning of the word, a baby with a mortal defect. Accordingly, the question returns. If a baby with a mortal defect is exempt from Pidyon ha'Ben, then why is one obligated to redeem a two-headed baby?

(a) RAV CHAIM SOLOVEITCHIK answers that a baby with two heads is not actually a Tereifah. Having two heads is not a mortal defect. The Gemara considers it a Tereifah only in its initial assumption, in the Havah Amina, when it asks that a Tereifah is exempt from Pidyon ha'Ben. The Gemara answers that a two-headed baby is not a Tereifah, and since the Torah requires that five Shekels be given for each head, ten Shekels must be given for a two-headed baby.

Rav Chaim explains the shift in the Gemara's understanding of the status of a two-headed baby. The Gemara initially assumes that what obligates a two-headed baby to be redeemed with two Pidyonos is the fact that two people are present in the firstborn baby. The Gemara questions this from the Halachah that a Tereifah is exempt. If the firstborn son is considered two sons, then each head is viewed as a separate person. However, one of the people (heads) has no body. A head with no body is a Tereifah, and a Tereifah is exempt from Pidyon.

The Gemara answers that the reason why a baby with two heads must be redeemed with two Pidyonos is not that there are two people present in this baby. Rather, the firstborn is only one person. Although he is only one person, he needs to be redeemed with two Pidyonos because the Torah says that the payment is according to the number of heads.

Once the Gemara teaches that the firstborn is only one person and not two, it is clear that there is no Tereifah present. Both heads are attached to one body, and, as one person, the baby is not a Tereifah.

The CHAZON ISH gives a similar answer. He explains that a person with two heads is not a Tereifah. The reason why the Gemara asks that a Tereifah is exempt from Pidyon ha'Ben is that the Gemara at that stage understands (from the Halachah that a Tereifah is exempt) that in order to be obligated, one must be a fully living person. The second head of a two-headed person is not a fully living person, since it has no body. The Gemara answers that in order to be obligated in two Pidyonos, it is not necessary that there be two fully living persons; one life is enough to obligate the two-headed baby to be redeemed with two Pidyonos. The Torah says that one pays according to the number of heads, even when those heads belong to a single life. Therefore, there is no question from the Halachah that a Tereifah is exempt, because a Tereifah is not fully alive, while a two-headed baby is fully alive. (Mordechai Zvi Dicker)

(b) The GILYON HA'SHAS (37a) cites the KOSNOS OR who answers as follows. A two-headed baby is a Tereifah because of the rule that "Kol Yeser k'Natul Dami," as Rabeinu Tam (in Tosfos here) writes. A Tereifah of "Yeser k'Natul" refers to a person or animal that has two of a certain vital organ that, normally, when removed causes the person or animal to die (see Insights to Chulin 58:6). The RASHBA writes that it is a Halachah l'Moshe mi'Sinai that although a person will live when the extra organ is removed (since he still has the original organ), he is considered a Tereifah. Even though the two-headed baby will live when the extra head is removed, he is still a Tereifah of "Yeser k'Natul," but not because he is going to die. The Gemara asks that since the Halachah is that a Tereifah is exempt from Pidyon, why must one pay two Pidyonos to redeem this firstborn?

The Gemara answers that it is true that the two-headed person is a Tereifah. However, the Halachah that a Tereifah is exempt from Pidyon ha'Ben does not apply to every type of Tereifah. Only a Tereifah that is going to die is exempt. A Tereifah due to the Halachah l'Moshe mi'Sinai of "Yeser k'Natul" is not exempt from Pidyon ha'Ben.