Adam Clarke on Genesis 42:9

Ye are spies - מרגלים אתם meraggelim attem, ye are footmen, trampers about, footpads, vagabonds, lying in wait for the property of others; persons who, under the pretense of wishing to buy corn, desire only to find out whether the land be so defenceless that the tribes to which ye belong (see Gen 42:11) may attack it successfully, drive out the inhabitants, and settle in it themselves; or, having plundered it, retire to their deserts. This is a frequent custom among the Arabs to the present day. Thus Joseph spake roughly to them merely to cover that warmth of affection which he felt towards them; and that being thus brought, apparently, into straits and dangerous circumstances, their consciences might be awakened to reflect on and abhor their own wickedness.