13יֵשׁ מְקוֹמוֹת שֶׁנָּהֲגוּ שֶׁיִּהְיוּ כָּל פֵּרוֹת מְנֻקִּים וּבְרוּרִים מִכָּל דָּבָר. וְשֶׁיִּהְיוּ הַיֵּינוֹת וְהַשְּׁמָנִים צְלוּלִין. וְלֹא יִמְכְּרוּ הַשְּׁמָרִים כְּלָל. וְיֵשׁ מְקוֹמוֹת שֶׁנָּהֲגוּ אֲפִלּוּ הָיוּ בָּהֶן מֶחֱצָה שְׁמָרִים. אוֹ שֶׁהָיוּ בְּפֵרוֹת מֶחֱצָה עָפָר אוֹ תֶּבֶן אוֹ מִין אַחֵר יִמָּכֵר כְּמוֹת שֶׁהוּא. לְפִיכָךְ הַבּוֹרֵר צְרוֹר מִתּוֹךְ גָּרְנוֹ שֶׁל חֲבֵרוֹ נוֹתֵן לוֹ דְּמֵי חִטִּים כְּשִׁעוּר צְרוֹר שֶׁבֵּרֵר. שֶׁאִלּוּ הִנִּיחוֹ הָיָה נִמְכָּר בְּמִדַּת חִטִּים. וְאִם תֹּאמַר יַחְזִירֶנּוּ הֲרֵי אָמְרוּ אָסוּר לְעָרֵב כָּל שֶׁהוּא:
There are places where it is customary for all produce to be sold when it has been cleaned and sifted, removing all foreign bodies, and for the wines and the oils to be clear, without selling any dregs at all. And there are other places where produce is sold even when there are half dregs, or there is half the amount of sand, straw or another substance in the produce. Therefore, in such a locale, if a person takes a stone from a colleague's grain heap, he must reimburse the owner as if the stone he took were wheat. For if he had left it there, it would have been sold as part of the measure of wheat.'If one would say, "Let him return the stone," this is forbidden, for it is forbidden to mix even the slightest amount of foreign substances into produce.