parshanut torah comment - Why does parshat bamidbar repeat census information?

It seems that the 3rd aliyah in Bamidbar needlessly repeats the information given in the 1st and second aliyah

First Aliyah: Lists the leaders of each tribe

Second Aliyah: gives us the census information for each tribe

Third Aliyah: Describes the order the Tribes camped in.

However, the third aliyah also retells us the leader of each tribe as well as the population of each tribe. Don't we already know that information from the first two aliyahs?

Answer

The repetition of the population figures:

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  Ibn Ezra (to 2:32) and Ramban (to 2:4) say that it underscores the fact that from the census (on the 1st of Iyar, Num. 1:1) until the next time they traveled (on the 20th of that month, ibid. 10:11), no one in such a vast multitude died (against all natural expectations) - so that the figures remained the same.

  
  

  [Malbim (to 2:2) says pretty much the same thing, though he takes the view that the figures in ch. 2 were the result of a separate census taken for the purpose of setting up the camp, not just reusing the earlier results.]

  
  


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  Abarbanel writes that this was done to tell us why each tribe was assigned to its particular location. Basically, he says, an army's lead unit ("what people call in the vernacular the 'avant-garde'") and rear unit have to be large in size to repel attackers, while the flanks can be smaller. In keeping with this, Yehudah's camp had the greatest number of people, Dan's the second largest, and the other two had fewer people.

  
  

The repetition of the names of the leaders:

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  Malbim (to 2:5) says that the second counting of the three tribes of Yissachar, Zevulun and Reuven was overseen by their respective nesi'im, and therefore each of these tribes' population is described with the word ופקדיו ("and his enumeration") - by contrast with the others, which are described with ופקודיהם ("and their enumeration"). So those three leaders had to be mentioned again. He doesn't say anything about the other nine (just that those tribes handled the re-counting themselves), but presumably once the Torah had to repeat the names of some, it continues the same throughout.

  
  


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  It's also possible (though I don't know any source for this) that with the information in ch. 1 we might have thought that they were designated only to oversee the census, but not to lead their respective tribes when traveling and encamping. Repeating their names in ch. 2 makes it clear that they are in charge for all purposes. (This might also explain the repetition of the census figures - to clarify the scope of each one's responsibility.)