392. Buying and Checking Tefillin

Tefillin, Mezuzah v’Sefer Torah 2:10

If one buys tefillin from a seller who is not expert in them, he must inspect them. If he bought 100 tefillin, he should inspect three - either two tefillin of the head and one of the arm or two tefillin of the arm and one of the head. If these are found to be acceptable, it can be assumed that sofer (scribe) is proficient. Once this has been established, all the tefillin are considered to be acceptable and they need not be individually inspected. However, if they are purchased in different packages, they must all be checked because we then assume that they came from different sofrim.

Tefillin, Mezuzah v’Sefer Torah 2:11

Once a person has written tefillin for himself, purchased them from an expert, or purchased them from a non-expert and had them inspected, and he has placed the parchments inside their leather compartments, the tefillin need not be checked ever again. As long as the boxes remain intact, they have a presumption that they are fit even after a number of years. We do not suspect that a letter may have faded or become perforated. Hillel the elder had tefillin that he received from his grandfather.