K’vod haRav, I have a few questions on keeping a spare pair of tefillin b’chezkas kashrus:
1. How often does one need to wear tefillin (e.g. a spare pair) to keep them b’chezkas kashrus? Is once a month sufficient?
2. Is it sufficient each time to wear them long enough to say krias Shma or does one have to wear them longer each time (30 minutes). Wearing them for davening is not a good option, since they are righty and I am lefty, and also the shel rosh is too small…
3. The shel rosh on this pair is too small for my head. Do I need to adjust it to fit my head properly in order to fulfill the wearing for chezkas kashrus purposes, or is it sufficient just to put the shel rosh on my head as-is.
1. The time of “thirty days” (once a month) is not mentioned by poskim in regard to this halachah, and it appears that this will not be sufficient for establishing the chezkas kashrus. Although there is room for doubt in this, it is correct to be stringent (see Mateh Yehuda, Siman 39; Halachah Berurah (Birur Halachah) 39:22).
2. It is sufficient to wear them for a short time. The idea is that they must be regularly worn, and the amount of time does not matter.
3. They must be worn in a way that fulfills the mitzvah (which is how the halachah is defined); if they are small to the degree that this will not fulfill the mitzvah, you should adjust the size.