Genesis 42:18-20

On the third day, Joseph said to them, “Do as I say and you will live. I am a man who respects God. If you are as honest as you say you are, then I will keep just one of your brothers here in confinement while the rest of you carry grain home for your starving families. You must return with your youngest brother so that I may verify your story, and that you may not die.” So they agreed to do so.