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Why did they send Pinchas and the Nesi'im (verse 14)?
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Malbim: They sent Pinchas to rebuke them for the betrayal of Hashem, and the 10 Nesi'im 1 to confront them for what pertains to Yisrael.
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Moshav Zekenim and Or ha Chayim (both on Bamidbar 34:19, citing R. Nisim Ga'on): After Zimri, Shimon did not have a Nasi again. (Perhaps even though Shimon's head was not called Nasi by himself, the verse calls them 10 Nesi'im because all the rest were Nesi'im. - PF)
