Genesis 42:9-19

9 Joseph also remembered the dreams that he had dreamed about them. He said to them, "You are spies; you have come to see the nakedness of the land!"
10 They said to him, "No, my lord; your servants have come to buy food.
11 We are all sons of one man; we are honest men; your servants have never been spies."
12 But he said to them, "No, you have come to see the nakedness of the land!"
13 They said, "We, your servants, are twelve brothers, the sons of a certain man in the land of Canaan; the youngest, however, is now with our father, and one is no more."
14 But Joseph said to them, "It is just as I have said to you; you are spies!
15 Here is how you shall be tested: as Pharaoh lives, you shall not leave this place unless your youngest brother comes here!
16 Let one of you go and bring your brother, while the rest of you remain in prison, in order that your words may be tested, whether there is truth in you; or else, as Pharaoh lives, surely you are spies."
17 And he put them all together in prison for three days.
18 On the third day Joseph said to them, "Do this and you will live, for I fear God:
19 if you are honest men, let one of your brothers stay here where you are imprisoned. The rest of you shall go and carry grain for the famine of your households,