Genesis 42:9-12, 14-17, 19-20

And Joseph remembered the dreams that he had dreamed of them. And he said to them, “You are spies; you have come to see the nakedness of the land.” They said to him, “No, my lord, your servants have come to buy food. We are all sons of one man. We are honest men. Your servants have never been spies.” He said to them, “No, it is the nakedness of the land that you have come to see.”

But Joseph said to them, “It is as I said to you. You are spies. By this you shall be tested: by the life of Pharaoh, you shall not go from this place unless your youngest brother comes here. Send one of you, and let him bring your brother, while you remain confined, that your words may be tested, whether there is truth in you. Or else, by the life of Pharaoh, surely you are spies.” And he put them all together in custody for three days.

if you are honest men, let one of your brothers remain confined where you are in custody, and let the rest go and carry grain for the famine of your households, and bring your youngest brother to me. So your words will be verified, and you shall not die.” And they did so.