Genesis 42:14-20

But Joseph said to them, “It is as I said to you. You are spies. By this you shall be tested: by the life of Pharaoh, you shall not go from this place unless your youngest brother comes here. Send one of you, and let him bring your brother, while you remain confined, that your words may be tested, whether there is truth in you. Or else, by the life of Pharaoh, surely you are spies.” And he put them all together in custody for three days. On the third day Joseph said to them, “Do this and you will live, for I fear God: if you are honest men, let one of your brothers remain confined where you are in custody, and let the rest go and carry grain for the famine of your households, and bring your youngest brother to me. So your words will be verified, and you shall not die.” And they did so.