Cross reference
Genesis 42:33
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 42:19-20
19 if ye be true men, let one of your brethren be bound in your prison-house; but go ye, carry grain for the famine of your houses:
20 and bring your youngest brother unto me; so shall your words be verified, and ye shall not die. And they did so.
Genesis 42:15
15 hereby ye shall be proved: by the life of Pharaoh ye shall not go forth hence, except your youngest brother come hither.