Tefillin and a Change in Handedness

QUESTION: The Gemarah (Menachos 37a) explains that tefillin shel yad (of the arm) is placed on the left hand because the Torah states (Shemos 13:16) that Tefillin should be bound “al yodcho”, on your arm. “Yodcho” is spelled in an unusual manner, with an extra letter “hei” at the end of the word. Chazal explain that “yodcho” can be read as two words, “yad keiho”, the weak arm, which is the left hand.

If someone was born a righty, but due to illness his right hand became weak, and now his left hand is stronger and more capable than his right hand, should he begin putting tefillin on his right arm since that is now yad keiho (the weaker hand)?

ANSWER: The Mordechai discusses a related case. If a person was born a righty but trained himself to become a lefty, on which hand should he put tefillin? The Mordechai quotes two opinions on this matter. (The Mordechai was a German posek. He was born in 1250 and was murdered with his wife and children in 1298 in a horrific mass pogrom known as the Rintfleisch massacre.) Magen Avrohom OC 27 cites the two opinions quoted in the Mordechai but leaves the issue unresolved. Rav Yechezkal Landau, in his commentary on Shulchan Aruch, Dagul Meirevava, writes that even those who hold that a righty cannot transform himself into a halachic lefty, would agree that if this occurred due to illness, then he would have the status of a lefty and tefillin would be placed on the right hand. Furthermore, the Mishnah Berurah (27:22 and Beiur Halacha) writes that although the Magen Avrohom appeared to leave the question unresolved, from other statements of the Magen Avrohom, it is clear he sides with those who consider the person a lefty, and that is the opinion of other poskim as well. It would seem that this is the accepted psak halacha. 

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The Gerald & Karin Feldhamer OU Kosher Halacha Yomis is dedicated to the memory of Rav Yisroel Belsky, zt"l, who served as halachic consultant for OU Kosher for more than 28 years; many of the responses in Halacha Yomis are based on the rulings of Rabbi Belsky. Subscribe to the Halacha Yomis daily email here.