Argument among poskim whether the mitzva of Pidyon Haben can be done through a representative, or is has to be done personally.
Our parsha seems to state that it could be done through a shliach, in that Moshe brought it to Aharon on behalf of the Bechors.
Answers that distinguish our parsha from general pidyon:
Our parsha was a mere delivery of money, which everyone allows through a shliach as long as the father personally says the nusach of pidyon; or
Moshe had the status of a Kohen at that time, and he was the podeh; or
everyone would agree that a kohen can receive on behalf of another kohen; or
the pidyon of the Midbar was singular and had different rules than the pidyon we do now.
The Rama (YD 305:10) brings a Rivash that one cannot do Pidyon Haben via an agent. The Rivash is in the Teshuvos (131), but he does not say this explicitly. He brings the Rambam that says that the form of Bracha when a father redeems his son is "Ahl pidyon" but when a person redeems himself it is "Lifdos". The Rivash explains that as far as the father is concerned, the mitzva could be done by another person, namely the son himself when he grows up, and for a mitzva that could be done by another person the proper bracha is "ahl." `When the father was not podeh the son, and the son grew up and is podeh himself, that pidyon can not be done by anyone else at all, and in such cases, the language of the bracha is "li..", not "ahl." We see that the Rivash holds that Pidyon cannot be done by a third party, a shliach.
Everyone argues with the Rama/Rivash. As the Aruch Hashulchan (sk 5) says, וכל גדולי עולם דחו דבריו and that all the poskim say that one does not have to be concerned about the Rama's shitta here at all. The Gaon there says that the whole thing is an error and that it's not even in the Rivash. (I don't know why he says that. Look at the link. It looks like it's there. Either he had a different Rivash or he holds that's not how to learn the Rivash.)
If you know the Aruch Hashulchan, you know that with that kind of setup, he usually takes the side of the chiddush. Indeed, the Aruch Hashulchan does say that there is a strong basis for saying that Pidyon cannot be done by a shliach, and that one should very much avoid doing so.
The Aruch Hashulchan also says that some people say pshat that even the Rama agrees that you can send the money via shliach, and he only meant that the father himself needs to say the nusach of pidyon. "Some people" happens to be, among others, Reb Akiva Eiger there in Shulchan Aruch. But the Aruch Hashulchan disagrees with that pshat in the Rama, and holds that the Rama prohibits using a Shliach even for the giving of the pidyon money to the Kohen.
So just like the shittas haRosh (Chulin 6:8) about Bris Millah, we have a serious argument about shlichus by Pidyon. The issue of what is called a mitzva she'b'gufo, starting with the Tosfos HaRid brought in the Ketzos in 382 and onward, is endless. But what is interesting is that in the first case of Pidyon, in our parsha, did the people deliver the money to the kohanim themselves? No. They did not. Bamidbar 4:49-51
Moshe Rabbeinu took the money and gave it to Aharon and sons. It seems clear from these psukim that Shlichus works by pidyon haben. I found that the Baal HaHafla'ah in Kesuvos 74 and in his Panim Yafos on the Chumash points this out as well, as does the Malbim here.
Is this a kashe on the Rivash? According to Reb Akiva Eiger that I mentioned above, and the Hafla'ah, it is not shver on the Rivash, because they hold that even the Rivash allows mere delivery of money via shliach, so long as the father says the nusach of pidyon. But the Aruch Hashulchan has some explaining to do, because he holds that even the delivery of the money has to be done by the father and not a shliach.
We can defend the Aruch Hashulchan by using the pshat which the Hafla'ah proposes but immediately rejects: that Shlichus does not work, and Moshe Rabbeinu took the money not as a shliach, but rather in his position as Kohen Gadol (as he is described in Zevachim 101b.) The Hafla'a rejected this because of the simple reading of the psukim in Chumash, which he understands to mean that Aharon's receipt was the pidyon, not Moshe's, and that Moshe served as a shliach, not as a podeh.
But even if the Hafla'ah is right, and Moshe acted as a shliach, I would still say that there is no kashe on the Aruch Hashulchan from here. Even if Shlichus doesn't work, that's only when it's not beyado, or in a case of מיגו דזכי לנפשיה. Since Moshe could have taken it, but instead chose to give it to Aharon and family, shlichus does work here.
(Note: migo and beyado, which I am using to explain why shlichus worked here although it doesn't usually work by pidyon, is debatable. Our problem is not shlichus of the kohen to take the money, it is with shlichus of the father to give the money. So one might argue that migo and beyado wouldn't help. The only migo and beyado would be if someone was beyado to be the father, not to be the Kohen. But I can live with this kashe.)
In fact, although the Hafla'ah rejects this option, others, including Reb Dovid Soloveichik (as brought in the Shai Latorah,) say that the pidyon was effected as soon as Moshe Rabbeinu took the money. This would answer the kashe on the Aruch Hashulchan.
But we have to examine this solution, that Moshe took the pidyon as Kohen Gadol. I don't know whether the din of pidyon by giving money to a Kohen is a din in Aharon and sons, the family that took over the avodah, which would exclude Moshe Rabbeinu, or a din in Kehuna, in actual ability to do avodah, which would include him. This probably is related to the Macholkes Rishonim whether a woman Kohenes can take the five Selaim to be podeh a child. (Rambam 1 Bikkurim 10- No, / Rashi Kiddushin 8a and Tosfos Pesachim 49b- Yes.)
Rabbi Dr. NJS, wrote to inform me that the Netziv in passuk 50 says that the fact that they gave all the money to Moshe and he gave it as a sum to the Kohanim, which eliminated tovas hana'a, shows that it was a hora'as sha'ah and so no proof can be derived ledoros. Reb Nachum also expressed his consternation that the Aruch Hashulchan quoted neither his brother in law (the Netziv during his first marriage to Rabbi Epstein's sister) nor his son in law (the Netziv during his second marriage to Rabbi Epstein's daughter) on this matter. But everything balances out in the end. The Aruch Hashulchan's own son, the Torah Temimah, never quotes his father.
He then suggested that instead of saying "hora'as sha'a," one might suggest an explanation for the difference between this and the regular pidyon. It was a demographic exchange. Yes, of course they had a lottery, and those who did not have a corresponding Levi had to take money out of their pockets and pay, but this was still primarily a threshold event which exchanged one group for another, and not primarily an individual obligation, as it became afterwards. Therefore, the money was davka given as a sum and it was given davka through a shliach. I was not willing to take achrayus for his pshat, but he showed me that in the Ramban (Shemos 13:11), the fundamental difference between Pidyon Midbar and Pidyon Doros is inescapable, to wit:
I found that the Ibn Ezra (3:45) also says like the Netziv, that the Pidyon in the Midbar was a singular event with halachos that are different than Pidyon Le'Doros.
Both the Netziv and the Ibn Ezra seem to be inconsistent with the Medrash Rabba here (only male Kohanim) and the Gemara in Menachos 37a-b (two-headed child), which use the Pidyon Midbar as a source for dinim of Pidyon Doros.
- Rivash- no shlichus on Pidyon Haben.
- Shver from Pidyon in Midbar via Moshe Rabbeinu.
- Some answer that this was mere delivery of money, which even Rivash allows, as long as father personally says nusach of Pidyon.
- Others say Rivash would not allow this either, so kashe remains.
- That Moshe took pidyon not as shliach, but he was the Podeh as Kohen Gadol (which raises interesting lomdishe questions, and might be related to issue of a Bas Kohen taking pidyon money).
- That even if Moshe didn't take as Kohen Gadol, and Aharon was the Podeh, but since Moshe could have been the Podeh as Kohen Gadol, even the Rivash would agree he can be a shliach (which also raises interesting lomdishe questions about migo and b'yado).
- Or, that Pidyon Midbar was different than Pidyon leDoros (which is not like the pashtus of the Medrash and the Gemara in Menachos).