Genesis 42:14-20

But Joseph said to them, “It is as I spoke to you, saying, ‘You are spies!’ In this manner you shall be tested: By the life of Pharaoh, you shall not leave this place unless your youngest brother comes here. Send one of you, and let him bring your brother; and you shall be kept in prison, that your words may be tested to see whether there is any truth in you; or else, by the life of Pharaoh, surely you are spies!” So he put them all together in prison three days. Then Joseph said to them the third day, “Do this and live, for I fear God: If you are honest men, let one of your brothers be confined to your prison house; but you, go and carry grain for the famine of your houses. And bring your youngest brother to me; so your words will be verified, and you shall not die.” And they did so.