You can usually tell a lot by a person who needs to swear just to confirm what they are saying is in fact true and accurate. I’ve had a friend who would have to swear after telling their story. It’s almost as if their words meant nothing until they stressed how serious and truthful they were by swearing to God.
Jesus, in the Sermon on the Mount, reminds us of the very same thing. Let your “Yes” be “Yes” and your “No,” “No.” The fact that you have to swear to something demonstrates that there is not enough weight in your own character to confirm what you are saying. Let this not be true amongst us.