1)
Why does the Torah insert the (otherwise superfluous) word "Echad"?
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Menachjos, 87b: To teach us that there was only one Isaron measure in the Beis-Hamikdash (a heaped one).
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To preclude from the opinion of R. Meir, who maintains that there were two, a heaped one and a regular one. See Torah Temimah, note 13.
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