Answer: Maran Ha’Shulchan Aruch (Chapter 8) writes that if one wears a Tallit and removes it with the intention of putting it back on immediately thereafter (such as one who lends his Tallit to a friend for several minutes), one must recite another blessing before wearing the Tallit again. The Rama writes that others say that as long as one had in mind originally to wear the tallit again, one does not recite another blessing. Most Acharonim agree with the Rama’s position on this matter and as long as one intends to wear the Tallit again very soon after removing it, one does not recite another blessing before wearing it again.
Although in general we follow all of the rulings of Maran Ha’Shulchan Aruch, Maran Ha’Chida writes that in instances such as these where many Poskim disagree with Maran, we must be concerned with the prohibition of reciting a blessing in vain even in opposition of Maran’s ruling. Thus, halachically speaking, as long as one had in mind originally to wear the Tallit again soon after removing it, one does not recite another blessing.
It would seem that the same law should apply to Mezuzah and since one had in mind to re-affix the Mezuzah when originally removing it, one should not recite another blessing when re-affixing it.
Nevertheless, these situations are not exactly similar, for regarding a Mezuzah, one cannot know for certain that he will re-affix it to the doorpost, for one is removing it to have it checked; if the Mezuzah turns out to be invalid, one will have to affix another Mezuzah to the doorpost. Thus, it is unclear whether or not one will end up re-affixing this Mezuzah. In a situation like this, even regarding a Tallit, one would be required to recite another blessing, such as if one removes his Tallit and is unsure if he will wear it again soon thereafter or not; in this situations, if one does decide to wear the Tallit again, one must recite a new blessing according to all opinions. Based on this, the same applies to Mezuzah and since one is unsure if he will actually be re-affixing this Mezuzah, when one does so, one must recite another “Likvo’a Mezuzah” blessing.
Although some Acharonim write that even so, one should not recite a second blessing upon re-affixing the Mezuzah, nevertheless, the above distinction, that regarding Mezuzah, one is unsure if he will re-affix the Mezuzah, is halachically sound and one must indeed recite another blessing upon re-affixing it. Hagaon Harav Binyamin Aruatz writes likewise in a response quoted in the Sefer Admat Kodesh and he adds that this is the custom he has seen by great and righteous people. He writes that he has spoken this matter over with the great Rabbeinu Gedalya Hayun and the latter agreed and proceeded to support his opinion. Maran Harav Ovadia Yosef zt”l adds that the Sefer Ha’Eshkol writes so explicitly.
Thus, halachically speaking, if one removes a Mezuzah from one’s doorpost in order to ascertain its Kashrut and has in mind to re-affix it on the doorpost, one must recite another “Likvo’a Mezuzah” blessing before re-affixing it.
