Because of the great sanctity of Tefillin, great care should be taken to
prevent them from falling on the floor. If they do fall, the custom is to
fast. If they are still in their pouch, it is sufficient to make a donation to
charity. Fasting, or a donation to charity, is required even when they fall by
accident, for the very fact that they fell is regarded as a sign that the
person who dropped them should do teshuva.
Regarding this halachah, there is no difference between Tefillin placed on
the arm and Tefillin placed on the head, or between the Tefillin of Rashi and
Rabbeinu Tam. There are those who fast even if the parshios alone fall on the
floor. Nevertheless, when a mezuzah falls on the floor it is customary to give
a small donation to charity rather than fast.
If the straps of the Tefillin fall on the floor, even though care should
be taken to prevent it, it is not customary to fast.
According to the Admor of Belz, the custom of fasting also applies when
Tefillin fall to the ground while covered by their case (usually made of
plastic) because the knot of the Tefillin is outside the case and, in contrast
to the rest of the strap, the sanctity of the knot is comparable to the
sanctity of the Tefillin. If the empty pouch falls to the ground, neither
fasting nor charity is required.
The custom of fasting applies even when the Tefillin fall from a height of
less than ten t’fachim
(about 1 meter).
One need not fast when Tefillin fall onto the surface of a table. If
Tefillin fall onto the stairs that ascend to the Aron HaKodesh, it is as
though they fell on the floor.
If a person drops his Tefillin, when should he fast? If he did not yet eat
or drink, he should fast on the day that the Tefillin fell, even though he did
not accept upon himself to fast on the previous day. But if he already ate or
drank on that day, he should fast on the following day.
Because of the weakness of the generation, many observe the custom of
fasting until noon, even if they drank before the morning prayers. Those for
whom the fast is difficult (especially if it would disrupt their Torah
learning) redeem it with a donation to charity.
According to some, the owner of Tefillin that fell should make a donation
to charity, even when the Tefillin do not fall from his hand, for he was
negligent in putting them in a place from which they might fall. A person who
sees another’s Tefillin fall is not required to fast.