John Gill Commentary Genesis 42:20

"and bring your youngest brother unto me; so shall your words be verified, and ye shall not die. And they did so." — Genesis 42:20 (ASV)

But bring your youngest brother to me upon their return for more corn. so shall your words be verified; that they were true men, and had no ill design upon the land, but had come only to buy corn. and you shall not die as spies, which they were otherwise threatened with, and as it is customary in all nations to put such to death when found out. and they did so: they left one of their brethren behind, carried corn to their houses or families in Canaan, and brought their brother Benjamin with them when they returned to Egypt.