Tefillin
Question
Hi! I see people in the Old City wearing Tefillin all day long. Is this not odd?
Answer
Shalom!
Thank you for your question.
You are referring to the "Zilberman" Yeshiva in the Old City. Yes, they wear tefillin all day long.
Indeed, although tefillin are generally only worn during Shacharit nowadays, it is actually a mitzva that is in effect all day long. In fact, in ancient times, tefillin were indeed worn all day long. This is essentially no different from today’s practice of wearing tzitzit all day long. Today, however, it is rare to see individuals wearing tefillin outside of the Shacharit service.
One of the reasons that people ceased wearing tefillin all day long was due to the nearly constant climate of anti-Semitism and anti-Semitic decrees that existed throughout the centuries of the Diaspora. In some places, in fact, the non-Jewish authorities forbade the wearing of tefillin at any time.
Although there is no justification for not putting on tefillin nowadays, the common practice of wearing them only for Shacharit is perfectly acceptable. This is because wearing tefillin requires one to have a guf naki (a clean body). A “clean body” refers to the prohibition against passing gas while wearing tefillin . One who suspects that he will have to pass gas while wearing tefillin should not put them on. So too, one who is suffering from a bowel disorder and expects that he will have to relieve himself repeatedly is exempt from wearing tefillin due to guf naki . Guf naki also requires us to keep a clean mind when wearing tefillin.
The reality nowadays is that most people simply cannot maintain a guf naki all day long and, as such, the rabbis decided not to require tefillin to be worn all day long. Instead, wearing tefillin was limited to the Shacharit service, so that one would be wearing tefillin when most important – when reciting the Shema and Shemoneh Esrei. It is assumed that most people can maintain a guf naki during this short amount of time.
SOURCES: Sukka 28a; Megilla 28; Ta’anit 20b; Shabbat 118b; OC 25:4, 37:2, 38:1,4; Sefer Hachinuch 421