Is one who wears tefillin exempt from other mitzvos?

When a person is involved in the fulfillment of one mitzvah, he is exempt from other mitzvos, even those of greater importance. Therefore, people who are involved with producing or selling Sta”m are exempt from wearing tefillin, except during Kriyas Shema and Shemoneh Esrei. If a customer arrives at the time of davening and this is the only time he can purchase the Sta”m, the seller/producer is exempt not only from wearing tefillin, but also from reciting Shema and Shemoneh Esrei. When a person is wearing tefillin, however, he is still obligated in other mitzvos. Simply wearing tefillin is not viewed as involvement in the mitzvah, and one can keep other mitzvos at the same time.

Is a seller of tefillin always exempt from other mitzvos?

One who is involved in a mitzvah is exempt from other mitzvos, even if he is being paid or receiving another fringe benefit for his involvement. Therefore, a seller of Sta”m is exempt even if he will make a profit on the sale. If his primary intent is to generate profits, however, he remains obligated in other mitzvos. This qualification only applies in cases of an indirect mitzvah, such as selling Sta”m. When one is involved in an actual mitzvah like hashovas aveidah, he is exempt from other mitzvos even if he is being paid for his service.

Is one who is learning Torah exempt from tefillin?

A person who is learning part of the Torah Shebichsav (Written Torah) is exempt from wearing tefillin throughout the day. The learning of Torah serves as an ois in place of the ois of tefillin. He should, however, wear tefillin when saying Kriyas Shema and Shemoneh Esrei. Some opinions hold that a person is exempt even when he is learning Torah Sheba’al Peh (Oral Torah).