Reply To: Beis Hamikdash

Because we are issuing a psak which will lead to a person who is factually a chalal doing avodah on Shabbos.

The Meginei Shlomo addresses that at the end.

You could make a similar argument for eishes ish; if beis din would be mattir her, there would be no actual issur, yet we do, when issuing the psak, take into account that there’s an issur s’kilah.

That’s not the argument that Tosafos is addressing. The argument is based on whether there will actually be eidus against the woman. In the eishes ish case, if eidim in fact come, there will vadai have been a violation of eishes ish which is an issur misa. There is no way for Beis Din to be mattir anything. In the shevuya case, if eidim in fact come, there will not vadai have been a violation of an issur misa. There will have been a violation of an issur lav (zonah), and if the kid does the avodah on Shabbos there will be an issur misa. However, as the Meginei Shlomo points out, a Beis Hamikdash would be a necessary prerequisite and that being the case, ???? ??? ????? ?? ???? ????? ???? ????? ???? ??? ?????? ??? ????? ?????? ????? (Kiddushin 71a). So certainly there would be no problem for the future generations, and there wouldn’t be a problem for the original kid either, because if the eidim come now (i.e. before Moshiach) then we will pasul the kid from doing the avoda and no harm will have been done. And if eidim come after Moshiach comes, it won’t matter because Eliyahu will have already resolved it.

That’s why I was mechadesh that Rabbeinu Tam is concerned that the Beis Hamikdash will be rebuilt without Eliyahu.