Reference for Menachot 6:7

הָעֹמֶר הָיָה מְנֻפֶּה בִּשְׁלשׁ עֶשְׂרֵה נָפָה. וּשְׁתֵּי הַלֶּחֶם בִּשְׁתֵּים עֶשְׂרֵה. וְלֶחֶם הַפָּנִים בְּאַחַת עֶשְׂרֵה. רַבִּי שִׁמְעוֹן אוֹמֵר, לֹא הָיָה לָהּ קִצְבָּה, אֶלָּא סֹלֶת מְנֻפָּה כָּל צָרְכָּהּ הָיָה מֵבִיא, שֶׁנֶּאֱמַר (ויקרא כד), וְלָקַחְתָּ סֹלֶת וְאָפִיתָ אֹתָהּ, עַד שֶׁתְּהֵא מְנֻפָּה כָּל צָרְכָּהּ:

The <i>omer</i>was sifted in thirteen sieves, the two loaves [of Shavuot] in twelve and the showbread in eleven. Rabbi Shimon said there was no fixed [number], rather flour that was sifted as much as necessary was brought as it says (Leviticus 24) "You shall take flour and bake it" - until it has been sifted as much as needed.

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