Commentary for Bava Batra 5:11
אָמַר רַבָּן שִׁמְעוֹן בֶּן גַּמְלִיאֵל, בַּמֶּה דְבָרִים אֲמוּרִים, בַּלַּח. אֲבָל בַּיָּבֵשׁ, אֵינוֹ צָרִיךְ. וְחַיָּב לְהַכְרִיעַ לוֹ טֶפַח. הָיָה שׁוֹקֵל לוֹ עַיִן בְּעַיִן, נוֹתֵן לוֹ גֵרוּמָיו, אֶחָד לַעֲשָׂרָה בַּלַּח וְאֶחָד לְעֶשְׂרִים בַּיָּבֵשׁ. מְקוֹם שֶׁנָּהֲגוּ לָמֹד בַּדַּקָּה, לֹא יָמֹד בַּגַּסָּה. בַּגַּסָּה, לֹא יָמֹד בַּדַּקָּה. לִמְחֹק, לֹא יִגְדֹּשׁ. לִגְדֹּשׁ, לֹא יִמְחֹק:
R. Shimon b. Gamliel said: When is this (the above) so? With wet (objects). But with dry, it is not necessary. And he (the seller) must lower (the balance) for him (the buyer) a handbreadth [for the weight of a litra or more, but not for less.] If he weighed it exactly, he gives him the due surplus, [a tenth of a litra for every ten litra, which is] one to ten [i.e., one in a hundred] in wet measure, and one to twenty [i.e., a half of a tenth for every twenty litra] in dry measure. In a place where the custom is to use small measure, one may not use large measure, [the buyer losing thereby, receiving only one "surplus" where he should have received many]; (where it is the custom) to use large measure, one may not use small measure. To strike off [what projects above the balance], one may not heap, [even for more money]; to heap, one may not strike off, [even for less money.]
Bartenura on Mishnah Bava Batra
English Explanation of Mishnah Bava Batra
[And a shopkeeper] must let the scales sink down a handbreadth [to the buyer’s advantage]. If he gave him an exact measure, he must give him his overweight, a tenth for liquid measures and a twentieth for dry measures.
Where the custom is to measure with small measures they should not measure with large measures and where the custom is to measure with large measures they should not measure with small measures.
Where the custom is to smooth down [what is in the measure] they should not heap it up, and [where the custom is] to heap it up, they should not smooth it down.
Mishnah eleven continues to deal with the weighing of produce.
Section one: Rabban Shimon ben Gamaliel qualifies the statements in the previous mishnah regarding cleaning out measures. These statements applied to measuring liquids, but measures used for dry goods need not be cleaned out with regular frequency, since the dry goods do not stick to the sides.
Section two: The custom was to let the buyer’s side of the scale, which contained the goods, sink one handbreadth lower than the seller’s side. If, however, one did not follow this custom, then the shopkeeper would be obligated to give the buyer either a tenth or a twentieth more than he purchased, depending on the nature of the produce.
Sections three and four: The last two sections teach that one must follow the customs that are typical in one’s place. This is true with regards to the size of the weights as well as the smoothing out or heaping up of the dry goods in the measuring cup. As long as people are consistent in their customs, buyers and sellers will know what they are doing and one will not cheat each other.