Genesis 42:16-19

42:16 One of you must go and get your brother, while the rest of you remain in prison. In this way your words may be tested to see if you are telling the truth. If not, then, as surely as Pharaoh lives, you are spies!” 42:17 He imprisoned them all for three days. 42:18 On the third day Joseph said to them, “Do as I say and you will live, for I fear God. 42:19 If you are honest men, leave one of your brothers confined here in prison while the rest of you go and take grain back for your hungry families.