John Gill Commentary Genesis 42:33

"And the man, the lord of the land, said unto us, Hereby shall I know that ye are true men: leave one of your brethren with me, and take [grain for] the famine of your houses, and go your way;" — Genesis 42:33 (ASV)

And the man, the lord of the country, said to us, by this shall I know that you [are] true [men]. This will be a proof and demonstration of it: leave one of your brothers [here] with me as an hostage; they do not say "bound in the prison", (Genesis 42:19), as Joseph did, because they would not grieve their father, at least would not tell him of it at once, lest it should too much affect him: and take [food for] the famine of your household, and be gone; that is, corn for the relief of their families, being distressed with a famine.