Keilim17: 9
הָאַמָּה שֶׁאָמְרוּ — בָּאַמָּה הַבֵּינוֹנִית. וּשְׁתֵּי אַמּוֹת הָיוּ בְשׁוּשַׁן הַבִּירָה, אַחַת עַל קֶרֶן מִזְרָחִית צְפוֹנִית, וְאַחַת עַל קֶרֶן מִזְרָחִית דְּרוֹמִית. שֶׁעַל קֶרֶן מִזְרָחִית צְפוֹנִית הָיְתָה יְתֵרָה עַל שֶׁל משֶׁה חֲצִי אֶצְבַּע. שֶׁעַל קֶרֶן מִזְרָחִית דְּרוֹמִית הָיְתָה יְתֵרָה עָלֶיהָ חֲצִי אֶצְבַּע, נִמְצֵאת יְתֵרָה עַל שֶׁל משֶׁה אֶצְבַּע. וְלָמָּה אָמְרוּ אַחַת גְּדוֹלָה וְאַחַת קְטַנָּה? אֶלָּא שֶׁהָאֻמָּנִין נוֹטְלִין בַּקְּטַנָּה וּמַחֲזִירִין בַּגְּדוֹלָה, כְּדֵי שֶׁלֹּא יָבוֹאוּ לִידֵי מְעִילָה.
The amah of which [the Rabbis] spoke is a medium amah. Two [one-] amah [measuring sticks] were [kept] in Shushan HaBirah, one at [its] northeastern corner, and one at [its] southeastern corner. [The one] at the northeastern corner was longer than [the amah] of Moses by a half-fingerbreadth. [The one] at the southeastern corner was longer than that one by [another] half-fingerbreadth; [this second measuring stick] is thus found to be longer than [the amah] of Moses by a full fingerbreadth. And why did [the Rabbis] speak of one large [amah measure] and one small [amah measure]? So that the craftsmen would take [contracts] according to the small [amah measure] and return [the finished products] according to the large [amah measure], in order that they should not come to [commit] me’ilah.