Can someone purchase a mezuzah case made by a non shomar Shabbos person if the person making the case assures you that it will not be made on shabbos? The question is significant because it’s an object used for a mitzvah. Naming keeping the mezuzah on the doorpost and safe, free from potential damage. A person wanting to do mitzvat lchachila as opposed to just doing them as a second thought. Also, even if someone learns the laws of mezuzah, he /or she might not be exposed to all the laws like a person who learns torah umnoso, potential poskim or Rabbis?
Thank you for your question.
It is permitted to buy the muzuza case, and you don’t have to be afraid that it might have been made on Shabbos. You are right, that the mezuza case is used to protect the mezuza, and also make the mezuza look nice, and therefore it has to eventually be put into shaimos. However, it is still not considered a mitzva object in the sense that if it was made through aveiro that it cannot be used, and that it ruins the mitzva. Regarding using an item that might have been made on Shabbos, it wouldn’t be different then any item bought from a non-religious Jew, that it might have been made on Shabbos. We are not worried about this, because it is only a safek, and because it is mixed into all the other things that the person made during the week.
M:B 154-14, Shulchan Shlomo ftnt. 5 to siman 318, Ashrei Hoish O:CH 2-24 (29)Oz NIdberu 1-52, Meohr Hashabbos1-18 ftnt. 107.