Rabban Shimon ben Gamliel said: In regard to what was this stated? In regard to moist [commodities]. However, [in the case] of dry [ones], it is not necessary.  He is obligated to overbalance [the scales] a handbreadth in [the buyer's] favor. [If] he was weighing for him evenly, he must give him the extra [weight]: one to ten for moist [commodities] and one to twenty for dry [ones]. [In] a place where it is customary to measure with a small [measure], he may not measure with a large one; with a large one, he may not measure with a small one. [In a place where it is customary] to level, he may not heap; to heap, he may not level.