Adam Clarke Bible Commentary

Commanded to fill their sacks - כליהם keleyhem, their vessels; probably large woolen bags, or baskets lined with leather, which, as Sir John Chardin says, are still in use through all Asia, and are called tambellet; they are covered with leather, the better to resist the wet, and to prevent dirt and sand from mixing with the grain. These vessels, of whatever sort, must have been different from those called שק sak in the twenty-seventh and following verses, which was probably only a small sack or bag, in which each had reserved a sufficiency of corn for his ass during the journey; the larger vessels or bags serving to hold the wheat or rice they had brought, and their own packages. The reader will at once see that the English word sack is plainly derived from the Hebrew.