Bible Verses About Oaths: Custom of swearing by the life of the king

Hereby ye shall be proved: By the life of Pharaoh ye shall not go forth hence, except your youngest brother come hither.

Send 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.