John Gill Commentary Genesis 42:34

"and bring your youngest brother unto me: then shall I know that ye are no spies, but that ye are true men: so will I deliver you your brother, and ye shall traffic in the land." — Genesis 42:34 (ASV)

And, bring your youngest brother to me Their brother Benjamin: then shall I know that you [are] no spies, but [that] you [are] true [men]; he knew they were no spies now, but true, honest, upright men, with respect to any designs upon the country; but then he should own and acknowledge them to be such, having such plain proof that what they said was true: [so] will I deliver your brother; their brother Simeon, who was left bound; though this circumstance they also here studiously conceal from their father: and you shall traffic in the land; not only for corn, but for any other commodity Egypt furnished its neighbours with.