Genesis 42:10-20

10 They said to him, "No, my lord, but your servants have come to buy food.
11 We are all one man's sons; we are honest men. Your servants are not spies."
12 He said to them, "No, but you have come to see the nakedness of the land."
13 They said, "We, your servants, are twelve brothers, the sons of one man in the land of Kana`an; and, behold, the youngest is this day with our father, and one is no more."
14 Yosef said to them, "It is like I told you, saying, 'You are spies.'
15 Hereby you shall be tested. By the life of Par`oh you shall not go forth from here, unless your youngest brother come here.
16 Send one of you, and let him get your brother, and you shall be bound, that your words may be tested, whether there is truth in you, or else by the life of Par`oh surely you are spies."
17 He put them all together into custody three days.
18 Yosef said to them the third day, "Do this, and live, for I fear God.
19 If you are honest men, then let one of your brothers be bound in your prison-house; but you go, carry grain for the famine of your houses.
20 Bring your youngest brother to me; so will your words be verified, and you won't die." They did so.