What is the rationale behind tashlumin?

Question

I understand that according to Masechet Brachot and the normative halacha, in certain cases, one who unintentionally missed saying a prayer service may "make up" that service by reciting the Shmoneh Esrei twice in the next service (Tashlumin). I know that there are many laws about exactly what to say and in which cases this opportunity exists, and whether this applies to the recitation of the Shma, and I know that even in the gemara, there is a discussion of whether this entire concept is actually efficacious or whether missed opportunities are missed.

But what I don't get is why this would ever be an option at all.

If we miss an obligation to perform a mitzvah, why would one think that we can "make good" by doing the mitzvah twice later? It isn't the case for lighting candles (though I know some women increase the number of candles they light permanently if they miss lighting on a Shabbat), and I can't think of another mitzvah where it IS the case. If I forget to bentch, I can't bentch twice after my next meal. If I forget to give matanot le'evyonim on one Purim, I can't give twice the next year. If I don't put on tefillin today, to I put them on twice tomorrow?

Why should there be a chance to make tashlumin, and why would it only be for Shmoneh Esrei? Is it just because "the gemara says so" or is there an underlying rule or logical principle involved?

Note -- I see this as related to, but not a duplicate of What does it mean to make up for prayers unavoidably missed - Tashlumin? because I see that question as based in the understanding of "Tashlumin" as "making up" whereas I see it as "completing an obligation" so I am less concerned with the object to whom one "makes up" and more with the notion that we can "complete" a mitzvah at some other time by doing it twice in any situation.

Answer 1

The basic scheme seems to be that Teffilos are רחמי and לואי שיתפלל כלל היום כולו, if only people would spend their entire day praying. Therefore a missed Teffila is not considered having passed it's time constraints. This is in stark contrast to a Teffila which was set up specially in place of a Korban such as Musaf. Once the proper time for that Tefilla passes, it's too late. See Tosafos in Brachos 26b s.v. איבעיא להו. This distinction between Mussaf and other Teffilos is brought in Shulchan Aruch 108:6.

There is another related point from Tshuvas Rashba brought in Prisha 1. The Aruch HaShulchan 13 also brings it when trying to explain the Mechaber in siff three who's words are based off this Rashba. The Rashba says the only time tashlumin works is when a person prays the teffila he is required to pray at that time, and then his last tefila which he messed up will also be excepted before Hashem.

The Prisha builds off this Rashba and says just like one cannot pray the Tashlumin too early, meaning before the chov, so too he cannot push it off later, meaning one must pray the Tashlumin immediately after the chov, without taking a long break between them. (With this he explains the importance of the statement of the Rivash to say Ashrei before the Tashlumin for mincha brought in Ramma siff two.)

The Aruch HaShulchan used a phrase based off the Rashba 'while one is involved with praying עוסק בתפילתו , he can make up his mistake from the last tefila'.

From both of these sources it seems that Tashlumin is an ability to squeeze the old missed Teffila through the opening of opportunity of acceptance along with the present Teffila. This would seemingly only make sense if Teffilos are Rachami which itself has no real time constraints as mentioned before, and not an act to be performed with a second chance clause.