Our parsha tells us that the principle of arvus started only after Bn"Y crossed into Eretz Yisrael.
I want to revisit a post from 20 years ago because of a chiddush my wife wanted to suggest on the parsha.
The gemara in Brachos has a safeik whether women are chayavos in birchas hamazon min hatorah or not. The Rosh writes that since this issue is unresolved, a woman may not be motzi a man in bentching. The principle that allows one person to be motzi another only works if the two share parallel chiyuvim. Since the woman's chiyuv may only be derabbanan and the man's chiyuv is d’oraysa, it doesn't work.
Asks the Rosh, why should this distinction in the levels of chiyuvim matter? This principle of arvus tells us that even if person A has already fulfilled their chiyuv and no longer has any obligation to do a mitzvah, that person can still be motzi person B. A man who ate a k’zayis (chiyuv derabbanan) can be motzi a man who ate k’dei seviya (chiyuv d’oraysa) because of this principle. In fact, in theory, even if person A ate nothing, he should be able to be motzi person B (l'maaseh we don't hold that way for different reasons). Therefore, by the same token, even if a woman’s chiyuv in bentching is only derabbanan, she should be able to be motzi a man.
Rosh answers with a tremendous chiddush: the principle of arvus does not apply to women.
The Dagul m’Revava raises a number of questions on this yesod of the Rosh, the most well known (O.C. 271) relating to the mitzvah of kiddush. According to the Magen Avraham, a man is yotzei his mitzvah of kiddush m’doraysa by reciting kiddush hayom in ma’ariv of Shabbos. How can a man be motzi his wife, who is chayeves in kiddush min hatorah, when he has already fulfilled his kiddush m’doraysa and the principle of arvus does not apply?
R’ Akiva Eiger disagrees with the Dagel m’Revava’s reading of the Rosh. The Rosh never meant that arvus does not extend to women. What the Rosh meant is in a case where women might not be obligated in the mitzvah at all, like bentching, then there is no arvus. Where women have a chiyuv, like the case of kiddush, the principle of arvus applies.
What is the nekudas ha'mahlokes between them? Yesh lachkor whether arvus is a din prati, a detail in each and every mitzvah, which allows someone who already was yotzei to do the mitzvah for someone who was not, or whether it is a din klali, a blanket rule that covers all mitzvos? The SM"G, for example, counts arvus as one of the 613 mitzvos. It is an independent din its own right, not a detail of each individual mitzvah. This would fit the Dagul m'Revava's position that either you are included in arvus or not; it's all or nothing. RAK"E, on the other hand, judges each mitzvah independently, and conditions arvus on whether or not a person has a chiyuv in that particular mitzvah or not, suggesting that it is a din prati.
What my wife wanted to suggest is that that arvus is not just linked to coming into Eretz Yisrael, but is linked to having a cheilek in Eretz Yisrael. The reason women are excluded from arvus is because, barring exceptions like Bnos Tzelafchad, they received no portion in the land.
I pointed out that if this is correct, it should also mean that a ger is not included in arvus since a ger has no cheilek in Eretz Yisrael. This is a machlokes even in Rishonim, see Tos Kiddusin 70b, Tos Nidah 13b.
R' Shternbruch has a teshuvah (Teshuvos v'Hanhagos 3:162) where he tries to soften this conclusion a bit. The question posed to him was regarding a bal toke'a who was a ger and wanted to go to the hospital on R"H after davening to blow shofar for those who were too sick to make it to shul. Interestingly, the people asking whether this is a good idea were only concerned with whether it is proper to have a non-meyuchas ger take the lead in this role. R" Shternbruch brushes that aside and points out that there is a more fundamental problem: if a ger is excluded from arvus, then he cannot be motzi anyone after he has done the mitzvah already!
R' Shternbruch comes up with a chiddush that I don't fully understand. He suggests that there are 2 dinim in arvus: 1) the question of whether a yachid can be motzi another yachid in mitzvos; 2) the question of whether gerim as a collective unit are included in the tzibur of klal Yisrael or not. He posits that the whole debate about whether gerim are included in arvus only relates to that second din, to the question of whether gerim as a unit are part of the tzibur or not. The Rashi in our parsha which speaks about arvus is speaking about whether Hashem holds the tzibur as a whole responsible for actions of individuals. That question hinges on how you define who is or who is not part of the tzibur. However, when it comes to an individual's right or ability to be motzi another individual in a mitzvah, there is no question that a ger can do so just as much as anyone else.
One of the arguments he makes is along the same lines as the point I raised to my wife: Why was RAK"E so convinced that women are included in arvus when Rishonim hold that geirim are not? I was willing to work with the idea that the machlokes Rishonim maybe parallels the macholes RAK"E and the D"R. R' Shternbruch's solution, based on his thesis, is that the question mixes apples and oranges. RAK"E is talking about the ability of a yachid to be motzi a yachid. The Rishonim are speaking about the question of who is included in the collective tzibur.
The Steipler has a piece where he mentions a proof for the D"mR against RAK"E from an unnamed talmid chacham. The gemara calculates that the number of britot that created arvus was 600,000 yotzei Mitzrayim x 600,000 each individual was responsible for. The reason geirim are exluded from arvus is because this number -- 600,000 (I'm rounding) -- does not include geirim. Well, but the same token, it does not include women either. The Steipler mentions that his son, R' Chaim, was doche this proof based on Tos (Nidah 13) that the number 600,000 is simply the people we know about, who were innumerated, not a grand total. According to R' Shternbruch (and I think he alludes to this question himself), the whole calculation does not make sense. The calculation is speaking about the responsibility of each individual member of Klal Yisrael towards each other individual member. According to R' Shternbruch, the exclusion of geirim means the collective of geirim as a group are not part of the tzibur, but that has no impact on the level of each person's individual arvus for his/her neighbor.
This gets to the heart of what bothers me most about this sevara. If there are two dinim in operation here, then there should be two independent sources for each. The source for arvus is the pasuk in our parsha that speaks about the brit that took effect after the entrance to Eretz Yisrael. If that refers only to the issue of defines who is part of the tzibur, then what is the source for the individual's responsibility for arvus on his/her friend?