Why does the Pasuk refer here to the census that took place when they left Egypt?
Rashi: To stress that the census here, like the census there, 1 should include all those from the age of twenty and onwards.
Seforno: To stress that the census here, like the census there, 2 should be done "le'Veis Avosam le'Mishpechosam".
Bechor Shor: Because inheritance of the land depends on Yotzei Mitzrayim, according to all opinions.
Alshich: This census was in order to testify about the Kosher Yichus of Bnei Yisrael (refer to 26:5:2:1). Do not say that youths below 20 were excluded, for their Yichus was tainted. Rather, it is because it is like the first Minyan.
Ha'amek Davar: Here it does not say how they will be counted. There, it says "be'Mishpar Sheimos le'Gulgelosam".
Rashi: With reference to the counting in Sh'mos 30:13, which is the main source of the Mitzvah ? See Sifsei Chachamim.
Seforno: See Bamidbar, 1:2.
Until what age were Yisrael counted?
Oznayim la'Torah (citing Midrash Rabah): Until the age of sixty - which we learn via a Gezeirah Shavah "va'Ma'alah" "va'Ma'alah" from Erchin. 1
Se Oznayim la'Torah citing Tosfos in Bava Basra.
QUESTIONS ON RASHI
Rashi writes that the Pasuk refers to the census after Yetzi'as Mitzrayim to teach us that they are counted from the age of twenty years and above. But our Pasuk explicitly says "mi'Ben Esrim Shanah va'Ma'alah"?
Hadar Zekenim: It is to teach us that also here, the census was performed via half-Shekalim (which they needed to give each year for the Korb'nos Tzibur - Meshech Chachmah). 1 The text of Rashi should say "Kol ha'Over? Yiten T'rumas Hashem." 2
See Sifsei Chachamim.
Since Elazar is mentioned, surely this was after Aharon died on Rosh Chodesh Av. If the Torah is in order, this is before Sefer Devarim, which begins on Rosh Chodesh Shevat. We give the [half-]Shekalim in Adar, for the coming year's Korbanos. Sefer Devarim begins on Rosh Chodesh Shevat! Perhaps the Torah is out of order, and this was just before Moshe died, on Adar 7. Or, it was not yet enacted to give to the Shekalim in Adar. Or, Hashem commanded to give the Shekalim early this year. (PF)
In our texts, Rashi concludes 'v'Gomer', i.e. he alludes to the continuation of the Pasuk! (PF)
