Genesis 42:15-16

15In this way you shall be tested: by the life of Pharaoh, you shall not leave this place unless your youngest brother comes here!

16Send 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.”