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Hilchos Tefillin 27 (page 74)

Why a Lefty Wears His Tefillin on His Right Arm
Someone Who Writes With One Hand and Performs the Rest of His Work With the Other Hand
Lefty Through Habituation


Why a lefty wears tefillin on his right arm 

A lefty who performs most of his work with his left arm/hand puts his tefillin on his right arm. Chazal derived this halacha in two ways. One is from the wording of "you shall tie them on your arm." The word used for arm in this pasuk is yadecha, written with a heh at the end to imply the weaker arm -- i.e. the tefillin should be tied on the weaker arm.  The other is from the juxtaposition of the two words ukshartam and uchsavtam (you shall tie and you shall write). By putting these two words together, the Torah showed that just as writing is done with the right hand, the tefillin should be tied with the right hand. Someone who is capable of doing his work with his right arm/hand but finds it easier to perform the work with his left hand is considered a lefty.

(???? ?, ?"? ??, ?? ????)

Someone who writes with one hand and performs the rest of his work with the other hand

There is a machlokes as to which of the previous derashos is primary. Many Rishonim hold that the halacha follows the opinion that tefillin are to be worn on the weaker hand. Therefore, someone who writes with one hand but does most of his work with the other should put his tefillin on his writing hand. Other Rishonim hold (and the Rama agrees with this opinion) that the tefillin are to be tied with the writing hand [onto the opposite arm]. According to this opinion, the person in the previous example would wear his tefillin on the arm which does most of the work. A third opinion holds that the halacha follows both derashos, and only someone who both writes and performs most of his work with his left hand can be considered a lefty.

(???? ?, ?"? ??-??, ????"? ?"? ??? ??"? ????; ??????? ??????? ????, 25)

Lefty through habituation

Someone who naturally used one hand for most melachos but then switched to use the other (due to training, illness, etc.) should consider the hand that he became habituated to use more to be his right hand. If for some reason he switched to using both hands, he is considered ambidextrous and should wear the tefillin on his left arm. There is an opinion that whichever side was his naturally dominant hand should be considered his right hand. The halacha follows the first opinion, but the second opinion may be considered in special circumstances. If part of someone's primary arm was severed, that arm becomes secondary and the tefillin should be placed on it if the tefillin area remained intact.

(?"? ?? ????, ????"? ?"? ????????; ??????? ??????? ????, 25)




  • According to most Rishonim, a chatzitza between the arm/head and the tefillin nullifies the mitzva. A second opinion holds that a chatzitza does not disqualify the mitzva. The halacha follows the first opinion.

  • The problem of chatzitza pertains to the bayis, the retzuos around the head, and the part that forms the knot of the shel yad.

  • Someone who has a bandage in the area of the shel rosh may put on his tefillin without a beracha. Similarly, if the shel yad is placed on a bandaged biceps, the beracha is recited just on the shel rosh as is done in the case of someone who has only a shel rosh.



  • The location of the shel rosh

  • 'The area of the hair'

  • Where on the neck should the knot be?