Genesis 42:15-16

42:15 You will be tested in this way: As surely as Pharaoh lives, you will not depart from this place unless your youngest brother comes here. 42:16 One of you must go and get your brother, while the rest of you remain in prison. In this way your words may be tested to see if you are telling the truth. If not, then, as surely as Pharaoh lives, you are spies!”