Genesis 42:15-16

15I will see if what you say is true. This is what I will do. I promise by the life of Pharaoh himself, I will not let you leave this place. You must first bring your youngest brother here. I will only let you go after that.

16One of you must go to bring your brother here. I will keep you others in prison. In that way I will know if what you said is true. If your youngest brother does not come, then I will certainly know that you are enemies!’