Genesis 42:16-19

16Send one from among yourselves to get your brother, while you remain confined, in order to test your words, to see whether the truth is with you. If not, by the life of Pharaoh, you’re definitely spies!”

17So he put them together in custody for three days.

18Then Joseph said to them on the third day, “Do this and you will live. I fear God.

19If you’re honest, let one of your brothers remain as a prisoner in the guardhouse where you’ve been, while you, go and bring grain for the hunger in your homes.