Genesis 42:18 Meaning

16Send one of you, and let him fetch your brother, and ye shall be kept in prison, that your words may be proved, whether there be any truth in you: or else by the life of Pharaoh surely ye are spies.

17And he put them all together into ward three days.

18And Joseph said unto them the third day, This do, and live; for I fear God:

19If ye be true men, let one of your brethren be bound in the house of your prison: go ye, carry corn for the famine of your houses:

20But bring your youngest brother unto me; so shall your words be verified, and ye shall not die. And they did so.