Mishnayos Bava Basra Perek 5 Mishnah 10

A wholesaler [hassiton] must clean his measuring vessels, which are used for measuring liquids such as oil and wine, once every thirty days, because the residue of the liquids sticks to the measure and reduces its capacity. And a homeowner who sells his goods must clean his measuring vessels only once every twelve months. Rabban Shimon ben Gamliel says: The matters are reversed. In the case of one who is constantly using his vessels for selling merchandise the residue does not adhere to the measuring vessel, and therefore a wholesaler must clean his measures only once a year. But in the case of a homeowner, who does not sell as often, the residue adheres to the measuring vessel; therefore, he must clean them every thirty days. A storekeeper, who constantly sells merchandise in small quantities, cleans his measuring vessels twice a week and cleans his weights once a week; and he cleans the pans of his scales after each and every weighing, to ensure that no merchandise has adhered to the pans, thereby increasing their weight.

הַסִּיטוֹן מְקַנֵּחַ מִדּוֹתָיו אַחַת לִשְׁלֹשִׁים יוֹם, וּבַעַל הַבַּיִת אַחַת לִשְׁנֵים עָשָׂר חֹדֶשׁ. רַבָּן שִׁמְעוֹן בֶּן גַּמְלִיאֵל אוֹמֵר, חִלּוּף הַדְּבָרִים. חֶנְוָנִי מְקַנֵּחַ מִדּוֹתָיו פַּעֲמַיִם בַּשַּׁבָּת, וּמְמַחֶה מִשְׁקְלוֹתָיו פַּעַם אַחַת בַּשַּׁבָּת, וּמְקַנֵּחַ מֹאזְנַיִם עַל כָּל מִשְׁקָל וּמִשְׁקָל: