Genesis 42:18-20

And on the third day Joseph said to them, Do this, if you would keep your lives: for I am a god-fearing man: If you are true men, let one of you be kept in prison, while you go and take grain for the needs of your families; And come back to me with your youngest brother, so that your words may be seen to be true, and you will not be put to death. This is what you are to do.