daf bit: Bava Batra 88

The torah commands us to have honest weights and measures. The mishna on today's daf discusses application. A wholesaler of items like oil and wine must clean his measures once in 30 days, because the residue diminishes the volume of what his customer takes away so he can't let it build up. A producer must clean his measures once in 12 months; the talmud assumes that he has fewer customers and fewer transactions than the wholesaler, so stuff doesn't build up as quickly. (R' Shimon ben Gamaliel reverses these, though, arguing that frequent use prevents some buildup and infrequent use allows more to stick.) A shopkeeper, who is presumed to have more customers than the wholesaler, must clean his measures twice a week, wipe his weights once a week, and clean his scales after every weighing. This last is because the pans in the scale are concave, so there's a place for stuff to pool. (88b)