You shall not have two differing weights in your bag, one heavy and one light.
Here is, I. A law against deceitful weights and measures: they must not only not use them, but they must not have them, not have them in the bag, not have them in the house (Deu 25:13, Deu 25:14); for, if they had them, they would be strongly tempted to use them.
Commenting on Deuteronomy 25:13-19
Thou shalt not have in thy bag divers weights,.... Or, "a stone and a stone" (y); it being usual, in those times and countries, to have their weights of stone, as it was formerly with us here; we still say, that such a commodity is worth so much per stone, a stone being of such a weight; now these were not to be different: a...
Thou shalt not have . . . divers weights--Weights were anciently made of stone and are frequently used still by Eastern shopkeepers and traders, who take them out of the bag and put them in the balance. The man who is not cheated by the trader and his bag of divers weights must be blessed with more acuteness than most of his fellows [ROBERTS]. (Compare Pro 16:11; Pro 20:10).