Genesis 42:14-20

Joseph said to them, “It is as I said to you, you are spies. In this way 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 [back home], and let him bring your brother [here], while [the rest of] you remain confined, so that your words may be tested, [to see] whether there is any truth in you [and your story]; or else, by the life of Pharaoh, certainly you are spies.” Then Joseph put them all in prison for three days. Now Joseph said to them on the third day, “Do this and [you may] live, for I fear God: if you are honest men, let one of your brothers be confined in your [place here in] prison; but as for the rest of you, go, carry grain for the famine in your households, but bring your youngest brother to me, so your words will be verified and you will not die.” And they did so.