The Ben Ish Chai in Shu”t Rav Peolim (Orach Chaim 4:2) discusses an incredible case, which took place in Bagdad. R’ Yehuda Ashkenazi came to visit and he realized that the tefillin everyone was wearing weren’t square. There is a halachah l’Moshe m’sinai, that the batim [boxes] of the tefillin need to be perfectly square. Somehow, this halachah wasn’t known to the people in Bagdad. After R’ Yehuda Ashkenazi realized the problem, he sat with the town sofar [scribe] and batim macher [one who makes tefillin boxes] and taught them how to make tefillin square. In the meantime, an announcement was made in all the shuls that the tefillin were all pasul and until the new tefillin were made they should put them on without making a berachah. The Ben Ish Chai, discusses how we look at such a thing, and if we really look at it as if they haven’t put on tefillin for all these years? He then continues to discuss what happens if one finds a letter missing from his tefillin after many years. Such a mistake could even be found after one dies, do we really look at it as if he never wore tefillin?
The Ben Ish Chai cites the Chida who in turn quotes the Shibolkay HaLeket who says that one gets rewarded according to his intention. The Shibolkay HaLeket quotes the Gemara in Makkos (11a) which says, that Rav saw the tefillin of Reb Chiya and they were sewn together with flax, which is pasul. Does this mean the holy Tanna R’ Chiya never fulfilled the mitzvah of tefillin? Certainly not, it must be that as long as one has kavonah to fulfill a mitzvah, he gets rewarded.
The truth is however, the above rayah is not such a good rayah, and both R’ Tzvi Pesach Frank (Har Tzvi 1:35) and R’ Ovadia refute it. There is a big difference between making a mistake in halachah, such as whether flax is suitable to be used in the sewing of tefillin and a mistake in metzius [reality]. The halachah which dictates that flax can’t be used in the sewing of tefillin is a halachah l’Moshe m’sinai, and according to R’ Ovadia, Reb Chiya never knew about the halachah l’Moshe m’sinai, and according to R’ Tzvi Pesach he held that flax was included in the halachah, however, when it comes to a missing letter etc. a person should have been more careful and done what he could to avoid such a pasul.
