Using a Mirror for Tefillin

Should we use a mirror to check the tefillin?

Shalom! 

Thank you for your question. 

Indeed, some authorities forbid the use of a mirror to ensure that one’s tefillin are centered properly. They argue that it is of no concern if one’s tefillin are not at the exact center of one’s head. This is because the mitzva is fulfilled even if the tefillin are slightly off-center. Indeed, the Talmud teaches that there is actually room on one’s head for two pairs of tefillin! Accordingly, even if one’s tefillin are not in the exact center of one’s head, they are certainly within the acceptable “tefillin zone.” The Sanzer Rebbe, Rav Chaim Halberstam, author of the halachic work Divrei Chaim, called the practice of using a mirror to ensure that one’s tefillin are positioned at the exact center of one’s head “the custom of fools.” 

Nevertheless, le'halcha it is permitted to use a mirror to ensure that one’s tefillin are properly positioned. So too, many authorities explain that the teaching of “there is room on the head for two pairs of tefillin” refers not to two pairs of tefillin sitting side by side, but rather, one behind (i.e., above) the other – both of which would have to be centered. According to this approach, it is important for the tefillin to be centered on one’s head as accurately as possible, and a mirror is a quick and efficient way to do this. Indeed, the Shulchan Aruch rules that the tefillin must lie exactly at the center of one’s head, between one’s eyes.  As such, using a mirror to check one’s tefillin is permissible. 

 Avoda Zara 44a; Eruvin 95b; Berura 32:182;Divrei Chaim, OC 2:6; Shulchan Aruch Harav, OC 27:18; Divrei Yoel, OC 4; Tzitz Eliezer 12:6:2.