Genesis 42:14-20

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