Adam Clarke Bible Commentary

Twenty shekels a day - The whole of the above grain, being ground, was to be formed into one mass, out of which he was to make three hundred and ninety loaves; one loaf for each day; and this loaf was to be of twenty shekels in weight. Now a shekel, being in weight about half an ounce, this would be ten ounces of bread for each day; and with this water to the amount of one sixth part of a hin, which is about a pint and a half of our measure. All this shows that so reduced should provisions be during the siege, that they should be obliged to eat the meanest sort of aliment, and that by weight, and their water by measure; each man's allowance being scarcely a pint and a half, and ten ounces, a little more than half a pound of bread, for each day's support.