Thematic Bible: Custom of swearing by the life of the king

But in this way will you be put to the test: by the life of Pharaoh, you will not go away from this place till your youngest brother comes here. Send one of your number to get your brother, and the rest of you will be kept in prison, so that your words may be tested to see if you are true; if not, by the life of Pharaoh, your purpose is certainly secret.