Genesis 42:13

10 And they said to him, Not so, my lord: your servants have come with money to get food.

11 We are all one man's sons, we are true men; we have not come with any secret purpose.

12 And he said to them, No, but you have come to see how poor the land is.

13 Then they said, We your servants are twelve brothers, sons of one man in the land of Canaan; the youngest of us is now with our father, and one is dead.

14 And Joseph said, It is as I said; you have come with some secret purpose;

15 But in this way will you be put to the test: by the life of Pharaoh, you will not go away from this place till your youngest brother comes here.

16 Send one of your number to get your brother, and the rest of you will be kept in prison, so that your words may be tested to see if you are true; if not, by the life of Pharaoh, your purpose is certainly secret.